Security document scanner

ABSTRACT

A sensing device for use with a security document is disclosed. The security document has disposed thereon or therein coded data including a plurality of coded data portions. Each coded data portion is indicative of an identity of the security document and a signature part. The signature part is a part of a digital signature of at least the identity. The sensing device has a sensor for sensing coded data portions and a processor. The processor determines, using sensed coded data portions, a sensed identity, a plurality of signature parts, and an identifier for each signature part, generates a sensed signature from the plurality of signature parts by arranging signature parts according to respective identifiers, determines a generated identity from the sensed signature, and authenticates the security document by comparing the sensed identity and the generated identity.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No11/863,253 filed on Sep. 28, 2007, now issued U.S. Pat. No. 7,681,800,which is a continuation of U.S. application Ser. No 11/041,650 filed onJan. 25, 2005, now U.S. Pat. No. 7,784,681, the entire contents of whichare now incorporated by reference.

FIELD OF THE INVENTION

The present invention broadly relates to a method and apparatus for theprotection of products and security documents using machine readabletags disposed on or in a surface of the product or security document.

CROSS REFERENCE TO OTHER RELATED APPLICATIONS

The following applications have been filed by the Applicant on Jan. 25,2005:

7,461,778 11/863,257 11/863,258 11/863,262 11/863,268 11/863,2697,637,419 7,676,382 7,464,879 11,863,263 7,469,819 7,484,101 7,472,2787,467,301

The disclosures of these co-pending applications are incorporated hereinby reference.

The following applications were filed by the Applicant on Jan. 25, 2005:

7,677,445 7,506,168 7,441,712 7,663,789 11/041,609 11/041,626 7,537,15711/041,624 7,395,963 7,457,961 11/041,580 7,467,300 7,467,299 7,565,542

The disclosures of these co-pending applications are incorporated hereinby reference.

Various methods, systems and apparatus relating to the present inventionare disclosed in the following co-pending applications and grantedpatents filed by the applicant or assignee of the present invention. Thedisclosures of all of these co-pending applications and granted patentsare incorporated herein by cross-reference.

7,249,108 6,566,858 6,331,946 6,246,970 6,442,525 7,346,586 09/505,9516,374,354 7,246,098 6,816,968 6,757,832 6,334,190 6,745,331 7,249,1097,197,642 7,093,139 7,509,292 10/636,283 10/866,608 7,210,038 7,401,22310/940,653 10/942,858 10/815,621 7,243,835 10/815,630 10/815,63710/815,638 7,251,050 10/815,642 7,097,094 7,137,549 10/815,618 7,156,29210/815,635 7,357,323 7,654,454 7,137,566 7,131,596 7,128,265 7,197,3747,175,089 10/815,617 7,537,160 7,178,719 7,506,808 7,207,483 7,296,7377,270,266 10/815,614 7,605,940 7,128,270 7,457,007 7,150,398 7,159,7777,450,273 7,188,769 7,097,106 7,070,110 7,243,849 6,623,101 6,406,1296,505,916 6,457,809 6,550,895 6,457,812 6,428,133 7,204,941 7,282,1647,465,342 7,148,345 7,416,280 6,746,105 7,246,886 7,128,400 7,108,3556,991,322 7,287,836 7,118,197 7,575,298 7,364,269 7,077,493 6,962,40210/728,803 7,147,308 7,524,034 7,118,198 7,168,790 7,172,270 7,229,1556,830,318 7,195,342 7,175,261 7,465,035 7,108,356 7,118,202 7,510,2697,134,744 7,510,270 7,134,743 7,182,439 7,210,768 7,465,036 7,134,7457,156,484 7,118,201 7,111,926 7,431,433 10/944,043 7,156,289 7,178,7187,225,979 09/575,197 7,079,712 6,825,945 7,330,974 6,813,039 7,190,4746,987,506 6,824,044 7,038,797 6,980,318 6,816,274 7,102,772 7,350,2366,681,045 6,678,499 6,679,420 6,963,845 6,976,220 6,728,000 7,110,1267,173,722 6,976,035 6,813,558 6,766,942 6,965,454 6,995,859 7,088,4596,720,985 7,286,113 6,922,779 6,978,019 6,847,883 7,131,058 7,295,8397,406,445 7,533,031 6,959,298 6,973,450 7,150,404 6,965,882 7,233,92409/575,181 7,593,899 7,175,079 7,162,259 6,718,061 7,464,880 7,012,7106,825,956 7,451,115 7,222,098 7,590,561 7,263,508 7,031,010 6,972,8646,862,105 7,009,738 6,989,911 6,982,807 7,518,756 6,829,387 6,714,6786,644,545 6,609,653 6,651,879 10/291,555 7,293,240 7,467,185 7,415,6687,044,363 7,004,390 6,867,880 7,034,953 6,987,581 7,216,224 7,506,1537,162,269 7,162,222 7,290,210 7,293,233 7,293,234 6,850,931 6,865,5706,847,961 10/685,583 7,162,442 10/685,584 7,159,784 7,557,944 7,404,1446,889,896 10/831,232 7,174,056 6,996,274 7,162,088 7,388,985 7,417,7597,362,463 7,259,884 7,167,270 7,388,685 6,986,459 10/954,170 7,181,4487,590,622 7,657,510 7,324,989 7,231,293 7,174,329 7,369,261 7,295,9227,200,591 11/020,106 11/020,260 11/020,321 11/020,319 7,466,4367,068,382 7,007,851 6,957,921 6,457,883 7,044,381 7,094,910 7,091,3447,122,685 7,038,066 7,099,019 7,062,651 6,789,194 6,789,191 7,529,9367,278,018 7,360,089 7,526,647 7,467,416 6,644,642 6,502,614 6,622,9996,669,385 6,827,116 7,011,128 7,416,009 6,549,935 6,987,573 6,727,9966,591,884 6,439,706 6,760,119 7,295,332 7,064,851 6,826,547 6,290,3496,428,155 6,785,016 6,831,682 6,741,871 6,927,871 6,980,306 6,965,4396,840,606 7,036,918 6,977,746 6,970,264 7,068,389 7,093,991 7,190,4917,511,847 7,663,780 10/962,412 7,177,054 7,364,282 10/965,733 10/965,93310/974,742 7,468,809 7,180,609 7,538,793 6,982,798 6,870,966 6,822,6396,474,888 6,627,870 6,724,374 6,788,982 7,263,270 6,788,293 6,946,6726,737,591 7,091,960 7,369,265 6,792,165 7,105,753 6,795,593 6,980,7046,768,821 7,132,612 7,041,916 6,797,895 7,015,901 7,289,882 7,148,64410/778,056 10/778,058 10/778,060 7,515,186 7,567,279 10/778,06210/778,061 10/778,057 7,096,199 7,286,887 7,400,937 7,474,930 7,324,8597,218,978 7,245,294 7,277,085 7,187,370 7,609,410 7,660,490 10/919,3797,019,319 7,593,604 7,660,489 7,043,096 7,055,739 7,233,320 6,830,1966,832,717 7,182,247 7,120,853 7,082,562 6,843,420 10/291,718 6,789,7317,057,608 6,766,944 6,766,945 7,289,103 7,412,651 7,299,969 7,108,1927,111,791 7,077,333 6,983,878 7,564,605 7,134,598 7,431,219 6,929,1866,994,264 7,017,826 7,014,123 7,134,601 7,150,396 7,469,830 7,017,8237,025,276 10/492,169 7,469,062 7,359,551 7,444,021 7,308,148 7,630,9627,630,554 10/510,391 7,660,466 7,526,128 6,957,768 7,456,820 7,170,4997,106,888 7,123,239 6,982,701 6,982,703 7,227,527 6,786,397 6,947,0276,975,299 7,139,431 7,048,178 7,118,025 6,839,053 7,015,900 7,010,1477,133,557 6,914,593 7,437,671 6,938,826 7,278,566 7,123,245 6,992,6626,593,166 7,132,679 6,940,088 10/727,162 7,377,608 7,399,043 7,121,6397,165,824 7,152,942 10/727,157 7,181,572 7,096,137 7,302,592 7,278,0347,188,282 7,592,829 10/727,180 10/727,179 10/727,192 10/727,27410/727,164 7,523,111 7,573,301 7,660,998 10/754,536 10/754,93810/727,160 7,369,270 6,795,215 7,070,098 7,154,638 6,805,419 6,859,2896,977,751 6,398,332 6,394,573 6,622,923 6,747,760 6,921,144 10/884,8817,092,112 7,192,106 7,374,266 7,427,117 7,448,707 7,281,330 10/854,5037,328,956 10/854,509 7,188,928 7,093,989 7,377,609 7,600,843 10/854,49810/854,511 7,390,071 10/854,525 10/854,526 7,549,715 7,252,353 7,607,7577,267,417 10/854,505 7,517,036 7,275,805 7,314,261 7,281,777 7,290,8527,484,831 10/854,523 10/854,527 7,549,718 10/854,520 7,631,190 7,557,94110/854,499 10/854,501 7,266,661 7,243,193 10/854,518 10/934,6286,454,482 6,808,330 6,527,365 6,474,773 6,550,997 7,093,923 6,957,9237,131,724 7,396,177 7,168,867 7,125,098

BACKGROUND

Security Document Counterfeiting

Counterfeiting of security documents, such as money, is an increasingproblem that now poses a real threat to the strength of global monetarysystems. Software and high quality photographic and printing technologyare making it easier for criminals to produce and pass counterfeit notesinto the monetary system. Counterfeit currency can be used to supportthe underground, untaxed economy, and it is a global threat that coulderode financial systems.

The main reason that counterfeiting remains a major concern is the easeand speed with which large quantities of counterfeit currency can beproduced using counterfeit software combined with high qualityphotographic and printing equipment. The occurrence of counterfeiting islikely to increase because these technologies are more readilyavailable, and the techniques are more easily understood by anincreasingly larger segment of the criminal population.

Whilst, these technologies do not reproduce the watermarks, colorshifting, embedded security threads, microprinting, and the general feelof the note, or the slightly raised print produced by engraved plates,in day-to-day transactions these features are often overlooked so thatcounterfeit notes are often accepted as legal tender. Counterfeit moneycan move through banks, money exchanges, casinos, and is even carriedoverseas, and there are growing opportunities for counterfeit currencyto be passed into the monetary system. Most of the large economiesaround the world are therefore now committed to introducing newtechnologies, as well as additional regulations and processes to makeidentification of counterfeit notes easier, to thereby reduce theincidence of counterfeit notes entering the monetary system.

Another concern is that there are governments who knowingly supportcounterfeiters, and some are complicit in producing counterfeitcurrency. A related problem is that all of the major U.S. and Europeanbanks have established multiple correspondent relationships throughoutthe world so they may engage in international financial transactions forthemselves and their clients in places where they do not have a physicalpresence. Many of these do not meet current regulatory or reportingrequirements, and therefore make it difficult to gain sufficientinformation to actively combat counterfeiting.

In addition to the growing problem of currency counterfeiting, the risksassociated with money laundering are also a major concern for manygovernments for two reasons:

-   -   1. Deregulation of global financial systems means that it is now        harder to combat money laundering; and    -   2. The funds involved in money laundering are increasing        rapidly.

There are two stages involved in money laundering: placement andlayering, and integration.

Placement is the movement of cash from its source and placing it intocirculation through financial institutions, casinos, shops, bureau dechange and other businesses, both local and abroad. Placement can becarried out through many processes including currency smuggling, bankcomplicity, deregulated currency exchanges, blending to enable fundsfrom illicit activities to be obscured in legal transactions, and usingthe proceeds to purchase less conspicuous assets.

The purpose of layering is to make it more difficult for law enforcementagencies to detect the trail of illegal proceeds. Layering methods caninclude converting cash to other monetary instruments such as banker'sdrafts and money orders, or selling assets bought with illicit funds.

The final stage of integration is the movement of previously launderedmoney into the economy, mainly through the banking system, to maketransactions appear to be normal business earnings.

The first thing to note about money laundering is that criminals preferto deal in cash because of its anonymity. In most financialtransactions, there is a financial paper trail to link the personinvolved. Physical cash, however, has disadvantages. It is bulky anddifficult to move. For example, 44 pounds of cocaine worth $1 million isequivalent to 256 pounds of street cash. The street cash is more thansix times the weight of the drugs. The existing payment systems and cashare both problems for criminals, even more so for large transnationalcrime groups. This is where criminals and terrorists are often mostvulnerable.

By limiting the opportunity for counterfeit notes, and funds fromillicit activities to enter the economy at the money placement andlayering phases, it becomes possible to restrict a wide range of moneylaundering activities.

To do this requires a detailed knowledge of cash flow movements that canonly be gained by introducing the ability to track and trace the flow ofindividual notes within the monetary system, and the ability to linklarge reportable cash transactions to an individual's identity.

As a consequence, governments have endeavored to:

-   -   Improve international co-operation through governments to        address money laundering and counterfeiting concerns; and,    -   Establish additional national controls for the distribution and        supply of currency within a country.

Concerted efforts by governments to fight money laundering have beengoing on for the past fifteen years. The main international agreementsaddressing counterfeit and money laundering include: the United NationsVienna Convention against Illicit Traffic in Narcotics Drugs andPsychotropic Substances (the Vienna Convention) and the 1990 Council ofEurope Convention on Laundering (Adopted in November 1990, the Councilof Europe Convention establishes a common criminal policy on moneylaundering. The convention lays down the principles for internationalco-operation among the contracting parties.).

The role of financial institutions in preventing and detecting moneylaundering has been the subject of pronouncements by the Basic Committeeon Banking Supervision, the European Union, and the InternationalOrganization of Securities Commissions.

In December 1988, the G-10's Basle Committee on Banking Supervisionissued a “statement of principles” with which the international banks ofmember states are expected to comply. These principles cover identifyingcustomers, avoiding suspicious transactions, and co-operating with lawenforcement agencies. In issuing these principles, the committee notedthe risk to public confidence in banks, and thus to their stability,that can arise if they inadvertently become associated with moneylaundering.

The “United Nations Convention against Transnational Organized Crime”was tabled for signing in December 2000. The Convention urgesgovernments to cooperate with one another in the detection,investigation and prosecution of money laundering. Signatories areobliged to reinforce requirements for customer identification,record-keeping and the reporting of suspicious transactions. Signatoriesare also recommended to set up financial intelligence units to collect,analyze and disseminate information.

Since the events of Sep. 11, 2001, UN Member States have emphasized thelinks between terrorism, transnational organized crime, theinternational drug trade and money laundering. The UN Security Counciladopted resolution 1373 (2001) and it established the Counter-TerrorismCommittee (CTC), which is mandated to monitor the implementation of theresolution urging States to prevent and suppress the financing ofterrorist acts.

Other potential macroeconomic consequences of unchecked money launderingthat have been noted by the International Monetary Fund (IMF) areinexplicable changes in money demand, contamination effects on legalfinancial transactions, and increased volatility of internationalcapital flow and exchange rates as a consequence of unanticipatedcross-border asset transfers. The latter point is especially importantand poses a significant risk to the EU financial system as moneylaundering has a direct effect on the Foreign Exchange Market (FOREX) ofan economy, which is vulnerable to the volume of cash involved in thetrade.

Banks are susceptible to risks from money launderers on several fronts.There is a thin line between a financial institution suspecting that itis being used to launder money and the institution becoming criminallyinvolved with the activity. Banks that are exposed as laundering moneyare likely to face costs associated with the subsequent loss of businesson top of vast legal costs. At the very least, the discovery of a banklaundering money for an organised crime syndicate is likely to generateadverse publicity for the bank. Banks passing counterfeit notes tocustomers will also result in declining business as clients takebusiness elsewhere. However, a much graver risk that banks face is thatof criminal prosecution for laundering money. EU laws and directivesstate that if a financial institution in the EU is found to be assistinga money launderer and failed to follow the appropriate procedures aslaid out by EU directives, the individual employee and respectivesupervisors, including company directors, are personally liable toimprisonment or fines. This is the reason why the EU directives on moneylaundering include the “know your customer” initiative.

As a result due diligence measures have been implemented by financialservice providers under regulatory supervision to ensure the integrityof those conducting business with the institution.

These consist of four sub-categories:

-   -   1) identification;    -   2) know your customer;    -   3) record keeping; and    -   4) suspicious activity reporting.

These are all time consuming and difficult to manage.

In addition to international efforts to combat counterfeiting and moneylaundering, most OECD governments have introduced a wide range ofdomestic statutes governing the distribution, and management ofcurrency. Some of these are needed to support international approaches,and others have been introduced to reduce local opportunities forterrorists or criminals to derive benefit from counterfeiting or moneylaundering activities. While it is not possible to consider all ofthese, a few U.S statutory requirements are considered here to highlightthe emerging requirements that any new currency validation and trackingsystem might be required to meet to support national and internationalobjectives.

Within the U.S., national distribution and supply of U.S. currency isregulated by the U.S Monetary Policy, and implemented by the FederalReserve and the Department of Treasury, and monitored by the SecretService. The Bureau of Engraving and Printing (BEP), which is a divisionof the U.S. Department of Treasury, serves as the United States'security printer. It produces the Nation's currency, most of its postagestamps, and other security documents (The first important distinction isthat while the Federal Reserve issues Federal Reserve notes, theTreasury issues coins. Consequently, the Federal Reserve determines theamount of new currency of each denomination to be printed annually bythe US Bureau of Engraving and Printing (BEP)).

In the case of currency, the Federal Reserve Banks verify all notesdeposited with them by the banking industry on a note-by-note basis.During this verification, deposited currency is counted for accuracy,counterfeit notes are identified, and unfit notes are destroyed. TheBEP, in conjunction with the Department of Treasury, Federal Reserve andSecret Service, are continuously working on changes that are required toprotect the integrity of the monetary system.

Additionally, the Internal Revenue Code (IRC) requires anyone involvedin a trade or business, except financial institutions, to reportcurrency received for goods or services in excess of $10,000. The BankSecrecy Act (BSA) mandates the reporting of certain currencytransactions conducted by financial institutions, the disclosure offoreign bank accounts, and the reporting of the transportation ofcurrency exceeding $10,000 across United States borders.

The Internal Revenue Service (IRS) is one of the key agencies involvedin money laundering investigations. Tax evasion, public corruption,health care fraud, money laundering and drug trafficking are allexamples of the types of crimes that revolve around cash. A financialinvestigation often becomes the key to a conviction.

In addition to providing physical protection to the leaders of theUnited States of America, the Secret Service has set as its highestinvestigative priority the identification and suppression of counterfeitcurrency production and distribution networks. With 60% of genuine U.S.currency circulating outside of the U.S, the dollar continues to be atarget for transnational counterfeiting activity.

The main objective of the U.S. Patriot Act 2001 is to amend certain lawswithin the constitution of the United States of America to assist withthe national and global fight against terrorism. These laws relate toreporting requirements for currency received in non-financial trade orbusiness. These include the name, address, and identificationinformation of the person from whom the currency was received, theamount of currency received, the date and nature of the transaction, andthe identification of the person filing the report.

In their effort to avoid using traditional financial institutions, manycriminals are forced to move large quantities of currency in bulk formthrough airports, border crossings, and other ports of entry where thecurrency can be smuggled out of the United States and placed in aforeign financial institution or sold on the black market. Thetransportation and smuggling of cash in bulk form may now be one of themost common forms of money laundering, and the movement of large sums ofcash is one of the most reliable warning signs of drug trafficking,terrorism, money laundering, racketeering, tax evasion and similarcrimes.

To support the above international and national initiatives, thetechnology industry has also initiated a number of programs. Forexample, IBM and Searchspace have joined forces to launch the IBMAnti-Money Laundering Service, a hosted computer service to help meetnew U.S. Patriot Act requirements, which requires firms to implement newtechnologies to detect and prevent money laundering schemes byterrorists and other criminals. Unisys also provides anti-moneylaundering and fraud detection services. These services have beenprovided to police forces and leading financial institutions.

Given the wide range of approaches adopted to support internationalco-operative efforts to limit terrorist and criminal activity, there isa growing recognition that organized crime is increasingly operatingthrough more fluid network structures rather than more formalhierarchies.

This therefore requires the use of new methods and technologies in orderto comply with the wide range of regulations and recommendations neededto combat laundering and counterfeiting. These new methods andtechnologies should make it easy to validate notes, automate many of thestatutory cash transaction reporting requirements, and provide thecapability for security agencies to detect crime patterns through cashflow tracking.

An existing solution to the problem involves the use of note trackingusing RFID integrated circuits.

Due to the Euro's broad cross-border reach, the European Central Bank(ECB) and criminal investigators in Europe are concerned about increasesin counterfeiting, as well as a possible increase in money laundering.There are now over 10 billion bank notes in circulation, with 4.5billion being held in reserve to accommodate potential leaps in demand.Last year, Greek authorities were confronted with 2,411 counterfeitingcases while authorities in Poland arrested a gang suspected of makingand putting over a million fake euros into circulation.

Because of these concerns, the application of RFID (Radio FrequencyIdentification) technology to paper currency is currently beinginvestigated by the European Central Bank and Hitachi.

Hitachi Ltd. announced plans in July 2003 for a integrated circuitdesigned for high denomination currency notes that would pack RFcircuitry and ROM in a 0.4-mm square circuit that is only 60 micronsthick. The Hitachi “mu-integrated circuit” will be capable of wirelesslytransmitting a 128-bit number when radio signals are beamed at it.Besides acting as a digital watermark, such RFID integrated circuitscould speed up routine bank processes such as counting. A stack of notescan be passed through a reader with the sum determined automatically,similar to the way that inventory is tracked in an RFID-based system.

However there are a number of difficulties that associated with such asolution.

First, there are concerns about the high costs associated with producingand integrating each integrated circuit into a note. Manufacturingprocesses are also considered a major hurdle to embedding a low-costantenna and integrated circuit in bank notes.

There are also concerns about the robustness of a integrated circuitsolution. Bank notes have a thickness of only about 80 microns. Once a60 micron thick RFID integrated circuit is connected to its antenna, itis likely to be well over 100 microns thick. They will therefore be atrisk of snagging on an object or surface, and being torn out of the notepaper. Notes rubbing against each other in a wallet may cause the RFIDintegrated circuits to tear out of the notes. Another major concern isthe robustness of the integrated circuit itself. Bank notes undergorepeated folding, they are accidentally put through washing machines,and they may receive large electrostatic shocks.

All of these will make it difficult for the issuers to guarantee thatintegrated circuits will continue to function properly for the expectedlife of the note. People are unlikely to accept that their notes areinvalid simply because the RFID integrated circuits have been torn outor damaged, so there will not be an expectation that all notes must haveRFID integrated circuits. So, a forger can pass off notes which neverhad integrated circuits simply by tearing small holes where theintegrated circuits have purportedly ‘snagged on something and been tornout’.

There are also concerns about privacy. With the potential to track andtrace cash, individuals may become concerned that cash will lose itsanonymity when buying goods. There are also concerns by privacyadvocates that a scanner in the hands of criminals could be used toremotely determine the amount of cash being carried by an individualwithout their knowledge. This could place them at risk of attack.

Thus, there are many factors that suggest that an RFID solution may notbe feasible for validating and tracking currency.

Surface Coding Background

The Netpage surface coding consists of a dense planar tiling of tags.Each tag encodes its own location in the plane. Each tag also encodes,in conjunction with adjacent tags, an identifier of the regioncontaining the tag. This region ID is unique among all regions. In theNetpage system the region typically corresponds to the entire extent ofthe tagged surface, such as one side of a sheet of paper.

The surface coding is designed so that an acquisition field of viewlarge enough to guarantee acquisition of an entire tag is large enoughto guarantee acquisition of the ID of the region containing the tag.Acquisition of the tag itself guarantees acquisition of the tag'stwo-dimensional position within the region, as well as othertag-specific data. The surface coding therefore allows a sensing deviceto acquire a region ID and a tag position during a purely localinteraction with a coded surface, e.g. during a “click” or tap on acoded surface with a pen.

The use of netpage surface coding is described in more detail in thefollowing copending patent applications, U.S. Ser. No. 10/815,647(docket number HYG001US), entitled “Obtaining Product Assistance” filedon 2 Apr. 2004; and U.S. Ser. No. 10/815,609 (docket number HYT001US),entitled “Laser Scanner Device for Printed Product Identification Cod”filed on 2 Apr. 2004.

Cryptography Background

Cryptography is used to protect sensitive information, both in storageand in transit, and to authenticate parties to a transaction. There aretwo classes of cryptography in widespread use: secret-key cryptographyand public-key cryptography.

Secret-key cryptography, also referred to as symmetric cryptography,uses the same key to encrypt and decrypt a message. Two parties wishingto exchange messages must first arrange to securely exchange the secretkey.

Public-key cryptography, also referred to as asymmetric cryptography,uses two encryption keys. The two keys are mathematically related insuch a way that any message encrypted using one key can only bedecrypted using the other key. One of these keys is then published,while the other is kept private. They are referred to as the public andprivate key respectively. The public key is used to encrypt any messageintended for the holder of the private key. Once encrypted using thepublic key, a message can only be decrypted using the private key. Thustwo parties can securely exchange messages without first having toexchange a secret key. To ensure that the private key is secure, it isnormal for the holder of the private key to generate the public-privatekey pair.

Public-key cryptography can be used to create a digital signature. Ifthe holder of the private key creates a known hash of a message and thenencrypts the hash using the private key, then anyone can verify that theencrypted hash constitutes the “signature” of the holder of the privatekey with respect to that particular message, simply by decrypting theencrypted hash using the public key and verifying the hash against themessage. If the signature is appended to the message, then the recipientof the message can verify both that the message is genuine and that ithas not been altered in transit.

Secret-key can also be used to create a digital signature, but has thedisadvantage that signature verification can also be performed by aparty privy to the secret key.

To make public-key cryptography work, there has to be a way todistribute public keys which prevents impersonation. This is normallydone using certificates and certificate authorities. A certificateauthority is a trusted third party which authenticates the associationbetween a public key and a person's or other entity's identity. Thecertificate authority verifies the identity by examining identitydocuments etc., and then creates and signs a digital certificatecontaining the identity details and public key. Anyone who trusts thecertificate authority can use the public key in the certificate with ahigh degree of certainty that it is genuine. They just have to verifythat the certificate has indeed been signed by the certificateauthority, whose public key is well-known.

To achieve comparable security to secret-key cryptography, public-keycryptography utilises key lengths an order of magnitude larger, i.e. afew thousand bits compared with a few hundred bits.

Schneier B. (Applied Cryptography, Second Edition, John Wiley & Sons1996) provides a detailed discussion of cryptographic techniques.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided asensing device for use with a security document, the security documenthaving disposed thereon or therein coded data including a plurality ofcoded data portions, each coded data portion being indicative of anidentity of the security document and a signature part, the signaturepart being a part of a digital signature of at least the identity, thesensing device including:

a sensor for sensing a plurality of coded data portions; and,

a processor for:

-   -   determining, using sensed coded data portions, a sensed        identity, a plurality of signature parts, and an identifier for        each signature part;    -   generating a sensed signature from the plurality of signature        parts by arranging signature parts according to respective        identifiers;    -   determining a generated identity from the sensed signature; and    -   authenticating the security document by comparing the sensed        identity and the generated identity.

Other aspects are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described with referenceto the accompanying drawings, in which:—

FIG. 1 is an example of a document including Hyperlabel encoding;

FIG. 2 is an example of a system for interacting with the Hyperlabeldocument of FIG. 1;

FIG. 3 is a further example of system for interacting with theHyperlabel document of FIG. 1;

FIG. 4. is a first example of a tag structure;

FIG. 5. is an example of a symbol unit cell for the tag structure ofFIG. 4;

FIG. 6. is an example of an array of the symbol unit cells of FIG. 5;

FIG. 7. is an example of symbol bit ordering in the unit cells of FIG.5;

FIG. 8. is an example of the tag structure of FIG. 4 with every bit set;

FIG. 9. is an example of tag types within a tag group for the tagstructure of FIG. 4;

FIG. 10. is an example of continuous tiling of the tag groups of FIG. 9;

FIG. 11. is an example of the orientation-indicating cyclic positioncodeword R for the tag group of FIG. 4;

FIG. 12. is an example of a local codeword A for the tag group of FIG.4;

FIG. 13. is an example of distributed codewords B, C, D and E, for thetag group of FIG. 4;

FIG. 14. is an example of a layout of complete tag group;

FIG. 15. is an example of a code word for the tag group of FIG. 4;

FIG. 16. is an example of an alternative tag group for the tag structureof FIG. 4;

FIG. 17. is a second example of a tag structure;

FIG. 18. is a third example of a tag structure;

FIG. 19 is an example of an item signature object model;

FIG. 20 is an example of Hyperlabel tags applied to a currency note;

FIG. 21 is an example of a note creation and distribution process;

FIG. 22. is an example of Scanning at Retailer interactions;

FIG. 23. is an example of Online Scanning interaction detail;

FIG. 24. is an example of Offline Scanning interaction details;

FIG. 25. is an example of netpage Pen Scanning interactions;

FIG. 26. is an example of netpage Pen Scanning interaction details;

FIG. 27. is an example of a Hyperlabel tag class diagram;

FIG. 28. is an example of a note ID class diagram

FIG. 29. is an example of an Object Description, ownership andaggregation class diagram;

FIG. 30. is an example of an Object Scanning History class diagram;

FIG. 31. is an example of scanner class diagram;

FIG. 32. is an example of an object ID hot list diagram;

FIG. 33. is an example of a valid ID range class diagram;

FIG. 34. is an example of Public Key List class diagram;

FIG. 35. is an example of a Trusted Authenticator class diagram;

FIG. 36. is an example of Tagging and Tracking Object Management;

FIG. 37. is an example of use of a currency counter;

FIG. 38. is an example of use of an automatic teller machine;

FIG. 39. is an example of use of a cash register;

FIG. 40. is an example of a Hyperlabel supermarket checkout;

FIG. 41. is an example of a handheld validity scanner;

FIG. 42. is an example of use of a handheld validity scanner;

FIG. 43. is an example of use of a sensing pen; and,

FIG. 44 is an example of a vending machine.

DETAILED DESCRIPTION OF THE DRAWINGS

The Netpage surface coding consists of a dense planar tiling of tags.Each tag encodes its own location in the plane. Each tag also encodes,in conjunction with adjacent tags, an identifier of the regioncontaining the tag. In the Netpage system, the region typicallycorresponds to the entire extent of the tagged surface, such as one sideof a sheet of paper.

Hyperlabel is the adaptation of the Netpage tags for use in unique itemidentification for a wide variety of applications, including securitydocument protection, object tracking, pharmaceutical security,supermarket automation, interactive product labels, web-browsing fromprinted surfaces, paper based email, and many others.

Using Memjet™ digital printing technology (which is the subject of anumber of pending U.S. patent applications including U.S. Ser. No.10/407,212), Hyperlabel tags are printed over substantially an entiresurface, such as a security document, bank note, or pharmaceuticalpackaging, using infrared (IR) ink. By printing the tags ininfrared-absorptive ink on any substrate which is infra-red-reflective,the near-infrared wavelengths, and hence the tags are invisible to thehuman eye but are easily sensed by a solid-state image sensor with anappropriate filter. This allows machine readable information to beencoded over a large portion of the note or other surface, with novisible effect on the original note text or graphics thereon. A scanninglaser or image sensor can read the tags on any part of the surface toperforms associated actions, such as validating each individual note oritem.

An example of such a hyperlabel encoded document, is shown in FIG. 1. Inthis example, the hyperlabel document consists of graphic data 2 printedusing visible ink, and coded data 3 formed from hyperlabel tags 4. Thedocument includes an interactive element 6 defined by a zone 7 whichcorresponds to the spatial extent of a corresponding graphic 8. In use,the tags encode tag data including an ID. By sensing at least one tag,and determining and interpreting the encoded ID using an appropriatesystem, this allows the associated actions to be performed.

In one example, a tag map is used to define a layout of the tags on thehyperlabel document based on the ID encoded within the tag data. The IDcan also be used to reference a document description which describes theindividual elements of the hyperlabel document, and in particulardescribes the type and spatial extent (zone) of interactive elements,such as a button or text field. Thus, in this example, the element 6 hasa zone 7 which corresponds to the spatial extent of a correspondinggraphic 8. This allows a computer system to interpret interactions withthe hyperlabel document.

In position indicating techniques, the ID encoded within the tag data ofeach tag allows the exact position of the tag on the hyperlabel documentto be determined from the tag map. The position can then be used todetermine whether the sensed tag is positioned in a zone of aninteractive element from the document description.

In object indicating techniques, the ID encoded within the tag dataallows the presence of the tag in a region of the document to bedetermined from the tag map (the relative position of the tag within theregion may also be indicated). In this case, the document descriptioncan be used to determine whether the region corresponds to the zone ofan interactive element.

An example of this process will now be described with reference to FIGS.2 and 3 which show how a sensing device in the form of a netpage orhyperlabel pen 101, which interacts with the coded data on a printedhyperlabel document 1, such as a security document, label, productpackaging or the like.

The hyperlabel pen 101 senses a tag using an area image sensor anddetects tag data. The hyperlabel pen 101 uses the sensed coded data togenerate interaction data which is transmitted via a short-range radiolink 9 to a relay 44, which may form part of a computer 75 or a printer601. The relay sends the interaction data, via a network 19, to adocument server 10, which uses the ID to access the documentdescription, and interpret the interaction. In appropriatecircumstances, the document server sends a corresponding message to anapplication server 13, which can then perform a corresponding action.

In an alternative embodiment, the PC, Web terminal, netpage printer orrelay device may communicate directly with local or remote applicationsoftware, including a local or remote Web server. Relatedly, output isnot limited to being printed by the netpage printer. It can also bedisplayed on the PC or Web terminal, and further interaction can bescreen-based rather than paper-based, or a mixture of the two.

Typically hyperlabel pen users register with a registration server 11,which associates the user with an identifier stored in the respectivehyperlabel pen. By providing the sensing device identifier as part ofthe interaction data, this allows users to be identified, allowingtransactions or the like to be performed.

Hyperlabel documents are generated by having an ID server generate an IDwhich is transferred to the document server 10. The document server 10determines a document description and then records an associationbetween the document description and the ID, to allow subsequentretrieval of the document description using the ID.

The ID is then used to generate the tag data, as will be described inmore detail below, before the document is printed by the hyperlabelprinter 601, using the page description and the tag map.

Each tag is represented by a pattern which contains two kinds ofelements. The first kind of element is a target. Targets allow a tag tobe located in an image of a coded surface, and allow the perspectivedistortion of the tag to be inferred. The second kind of element is amacrodot. Each macrodot encodes the value of a bit by its presence orabsence.

The pattern is represented on the coded surface in such a way as toallow it to be acquired by an optical imaging system, and in particularby an optical system with a narrowband response in the near-infrared.The pattern is typically printed onto the surface using a narrowbandnear-infrared ink.

In the Hyperlabel system the region typically corresponds to the surfaceof an entire product item, or to a security document, and the region IDcorresponds to the unique item ID. For clarity in the followingdiscussion we refer to items and item IDs (or simply IDs), with theunderstanding that the item ID corresponds to the region ID.

The surface coding is designed so that an acquisition field of viewlarge enough to guarantee acquisition of an entire tag is large enoughto guarantee acquisition of the ID of the region containing the tag.Acquisition of the tag itself guarantees acquisition of the tag'stwo-dimensional position within the region, as well as othertag-specific data. The surface coding therefore allows a sensing deviceto acquire a region ID and a tag position during a purely localinteraction with a coded surface, e.g. during a “click” or tap on acoded surface with a pen.

A wide range of different tag structures can be used, and some exampleswill now be described.

First Example Tag Structure

FIG. 4 shows the structure of a complete tag. Each of the four blackcircles is a target. The tag, and the overall pattern, has four-foldrotational symmetry at the physical level.

Each square region represents a symbol, and each symbol represents fourbits of information.

FIG. 5 shows the structure of a symbol. It contains four macrodots, eachof which represents the value of one bit by its presence (one) orabsence (zero).

The macrodot spacing is specified by the parameter s throughout thisdocument. It has a nominal value of 143 μm, based on 9 dots printed at apitch of 1600 dots per inch. However, it is allowed to vary by ±10%according to the capabilities of the device used to produce the pattern.

FIG. 6 shows an array of nine adjacent symbols. The macrodot spacing isuniform both within and between symbols.

FIG. 7 shows the ordering of the bits within a symbol. Bit zero is theleast significant within a symbol; bit three is the most significant.Note that this ordering is relative to the orientation of the symbol.The orientation of a particular symbol within the tag is indicated bythe orientation of the label of the symbol in the tag diagrams. Ingeneral, the orientation of all symbols within a particular segment ofthe tag have the same orientation, consistent with the bottom of thesymbol being closest to the centre of the tag.

Only the macrodots are part of the representation of a symbol in thepattern. The square outline of a symbol is used in this document to moreclearly elucidate the structure of a tag. FIG. 8, by way ofillustration, shows the actual pattern of a tag with every bit set. Notethat, in practice, every bit of a tag can never be set.

A macrodot is nominally circular with a nominal diameter of (5/9)s.However, it is allowed to vary in size by ±10% according to thecapabilities of the device used to produce the pattern.

A target is nominally circular with a nominal diameter of (17/9)s.However, it is allowed to vary in size by ±10% according to thecapabilities of the device used to produce the pattern.

The tag pattern is allowed to vary in scale by up to ±10% according tothe capabilities of the device used to produce the pattern. Anydeviation from the nominal scale is recorded in the tag data to allowaccurate generation of position samples.

Each symbol shown in the tag structure in FIG. 4 has a unique label.Each label consists an alphabetic prefix and a numeric suffix.

Tag Group

Tags are arranged into tag groups. Each tag group contains four tagsarranged in a square. Each tag therefore has one of four possible tagtypes according to its location within the tag group square. The tagtypes are labelled 00, 10, 01 and 11, as shown in FIG. 9.

Each tag in the tag group is rotated as shown in the figure, i.e. tagtype 00 is rotated 0 degrees, tag type 10 is rotated 90 degrees, tagtype 11 is rotated 180 degrees, and tag type 01 is rotated 270 degrees.

FIG. 10 shows how tag groups are repeated in a continuous tiling oftags. The tiling guarantees the any set of four adjacent tags containsone tag of each type.

Orientation-Indicating Cyclic Position Code

The tag contains a 2⁴-ary (4, 1) cyclic position codeword which can bedecoded at any of the four possible orientations of the tag to determinethe actual orientation of the tag. Symbols which are part of the cyclicposition codeword have a prefix of “R” and are numbered 0 to 3 in orderof increasing significance.

The cyclic position codeword is (0, 7, 9, E₁₆). Note that it only usesfour distinct symbol values, even though a four-bit symbol has sixteenpossible values. During decoding, any unused symbol value should, ifdetected, be treated as an erasure. To maximise the probability oflow-weight bit error patterns causing erasures rather than symbolerrors, the symbol values are chosen to be as evenly spaced on thehypercube as possible.

The minimum distance of the cyclic position code is 4, hence itserror-correcting capacity is one symbol in the presence of up to oneerasure, and no symbols in the presence of two or more erasures.

The layout of the orientation-indicating cyclic position codeword isshown in FIG. 11.

Local Codeword

The tag locally contains one complete codeword which is used to encodeinformation unique to the tag. The codeword is of a punctured 2⁴-ary(13, 7) Reed-Solomon code. The tag therefore encodes up to 28 bits ofinformation unique to the tag.

The layout of the local codeword is shown in FIG. 12.

Distributed Codewords

The tag also contains fragments of four codewords which are distributedacross the four adjacent tags in a tag group and which are used toencode information common to a set of contiguous tags. Each codeword isof a 2⁴-ary (15, 11) Reed-Solomon code. Any four adjacent tags thereforetogether encode up to 176 bits of information common to a set ofcontiguous tags.

The layout of the four complete codewords, distributed across the fouradjacent tags in a tag group, is shown in FIG. 13. The order of the fourtags in the tag group in FIG. 13 is the order of the four tags in FIG.9.

FIG. 14 shows the layout of a complete tag group.

Reed-Solomon Encoding

Local Codeword

The local codeword is encoded using a punctured 2⁴-ary (13, 7)Reed-Solomon code. The code encodes 28 data bits (i.e. seven symbols)and 24 redundancy bits (i.e. six symbols) in each codeword. Itserror-detecting capacity is six symbols. Its error-correcting capacityis three symbols.

As shown in FIG. 15, codeword coordinates are indexed in coefficientorder, and the data bit ordering follows the codeword bit ordering.

The code is a 2⁴-ary (15, 7) Reed-Solomon code with two redundancycoordinates removed. The removed coordinates are the most significantredundancy coordinates.

The code has the following primitive polynominal:p(x)=x ⁴ +x+1  (EQ 1)

The code has the following generator polynominal:g(x)=(x+α)(x+α ²) . . . (x+α ⁸)  (EQ 2)Distributed Codewords

The distributed codewords are encoded using a 2⁴-ary (15, 11)Reed-Solomon code. The code encodes 44 data bits (i.e. eleven symbols)and 16 redundancy bits (i.e. four symbols) in each codeword. Itserror-detecting capacity is four symbols. Its error-correcting capacityis two symbols.

Codeword coordinates are indexed in coefficient order, and the data bitordering follows the codeword bit ordering.

The code has the same primitive polynominal as the local codeword code.

The code has the following generator polynominal.g(x)=(x+α)(x+α ²) . . . (x+α ⁴)  (EQ 3)Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and yrespectively. When the positive x axis points to the right then thepositive y axis points down.

The surface coding does not specify the location of the tag coordinatespace origin on a particular tagged surface, nor the orientation of thetag coordinate space with respect to the surface. This information isapplication-specific. For example, if the tagged surface is a sheet ofpaper, then the application which prints the tags onto the paper mayrecord the actual offset and orientation, and these can be used tonormalise any digital ink subsequently captured in conjunction with thesurface.

The position encoded in a tag is defined in units of tags. Byconvention, the position is taken to be the position of the centre ofthe target closest to the origin.

Tag Information Content

Field Definitions

Table 1 defines the information fields embedded in the surface coding.Table 2 defines how these fields map to codewords.

TABLE 1 Field definitions width field (bits) description per tag xcoordinate 9 or 13 The unsigned x coordinate of the tag allows maximumcoordinate values of approximately 0.9 m and 14 m respectively. ycoordinate 9 or 13 The unsigned y coordinate of the tag allows maximumcoordinate values of approximately 0.9 m and 14 m respectively activearea flag 1 b′1′ indicates whether the area (the diameter of the areantered on the tag, is nominally 5 times the diagonal size of the tag)immediately surrounding the tag intersects an active area data fragmentflag 1 A flag indicating whether a data fragment is present (see nextfield). b′1′ indicates the presence of a data fragment. If the datafragment is present then the width of the x and y coordinate fields is9. If it is absent then the width is 13. data fragment 0 or 8  Afragment of an embedded data stream. per tag group (i.e. per region)encoding format 8 The format of the encoding. 0: the present encodingOther values are reserved. region flags 8 Flags controlling theinterpretation of region data. 0: region ID is an EPC 1: region hassignature 2: region has embedded data 3: embedded data is signatureOther bits are reserved and must be zero. tag size ID 8 The ID of thetag size. 0: the present tag size the nominal tag size is 1.7145 mm,based on 1600 dpi, 9 dots per macrodot, and 12 macrodots per tag Othervalues are reserved. region ID 96  The ID of the region containing thetags. signature 36  The signature of the region. high-order 4 The widthof the high-order part of the x and coordinate width y coordinates ofthe tag. (w) high-order x 0 to 15 High-order part of the x coordinate ofthe coordinate tag expands the maximum coordinate values toapproximately 2.4 km and 38 km respectively high-order y 0 to 15High-order part of the y coordinate of the coordinate tag expands themaximum coordinate values to approximately 2.4 km and 38 kmrespectively. CRC 16  A CRC of tag group data.

An active area is an area within which any captured input should beimmediately forwarded to the corresponding hyperlabel server forinterpretation. This also allows the hyperlabel server to signal to theuser that the input has had an immediate effect. Since the server hasaccess to precise region definitions, any active area indication in thesurface coding can be imprecise so long as it is inclusive.

The width of the high-order coordinate fields, if non-zero, reduces thewidth of the signature field by a corresponding number of bits. Fullcoordinates are computed by prepending each high-order coordinate fieldto its corresponding coordinate field.

TABLE 2 Mapping of fields to codewords codeword field codeword bitsfield width bits A 12:0  x coordinate 13 all 12:9  data fragment 4 3:025:13 y coordinate 13 all 25:22 data fragment 4 7:4 26 active area flag1 all 27 data fragment flag 1 all B 7:0 encoding format 8 all 15:8 region flags 8 all 23:16 tag size ID 8 all 39:24 CRC 16 all 43:40high-order coordinate 4 3:0 width (w) C 35:0  signature 36 all (35-w):(36-2w) high-order x coordinate w all    35:(36-w) high-order ycoordinate w all 43:36 region ID 8 7:0 D 43:0  region ID 44 51:8  E43:0  region ID 44 95:52Embedded Data

If the “region has embedded data” flag in the region flags is set thenthe surface coding contains embedded data. The data is encoded inmultiple contiguous tags' data fragments, and is replicated in thesurface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partialscan of the surface coding containing the embedded data can besufficient to retrieve the entire data. The scanning system reassemblesthe data from retrieved fragments, and reports to the user whensufficient fragments have been retrieved without error.

As shown in Table 3, a 200-bit data block encodes 160 bits of data. Theblock data is encoded in the data fragments of a contiguous group of 25tags arranged in a 5×5 square. A tag belongs to a block whose integercoordinate is the tag's coordinate divided by 5. Within each block thedata is arranged into tags with increasing x coordinate withinincreasing y coordinate.

A data fragment may be missing from a block where an active area map ispresent. However, the missing data fragment is likely to be recoverablefrom another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of acontiguous set of blocks arranged in a rectangle. The size of thesuperblock is encoded in each block. A block belongs to a superblockwhose integer coordinate is the block's coordinate divided by thesuperblock size. Within each superblock the data is arranged into blockswith increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as itwill fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise typeinformation, more precise size information, and more extensive errordetection and/or correction data.

TABLE 3 Embedded data block field width description data type 8 The typeof the data in the superblock. Values include: 0: type is controlled byregion flags 1: MIME Other values are TBA. superblock width 8 The widthof the superblock, in blocks. superblock height 8 The height of thesuperblock, in blocks. data 160 The block data. CRC 16 A CRC of theblock data. total 200

It will be appreciated that any form of embedded data may be used,including for example, text, image, audio, video data, such as productinformation, application data, contact data, business card data, anddirectory data.

Region Signatures

If the “region has signature” flag in the region flags is set then thesignature field contains a signature with a maximum width of 36 bits.The signature is typically a random number associated with the region IDin a secure database. The signature is ideally generated using a trulyrandom process, such as a quantum process, or by distilling randomnessfrom random events.

In an online environment the signature can be validated, in conjunctionwith the region ID, by querying a server with access to the securedatabase.

If the “region has embedded data” and “embedded data is signature” flagsin the region flags are set then the surface coding contains a 160-bitcryptographic signature of the region ID. The signature is encoded in aone-block superblock.

In an online environment any number of signature fragments can be used,in conjunction with the region ID and optionally the random signature,to validate the signature by querying a server with knowledge of thefull signature or the corresponding private key.

In an offline (or online) environment the entire signature can berecovered by reading multiple tags, and can then be validated using thecorresponding public signature key.

Signature verification is discussed in more detail below.

Mime Data

If the embedded data type is “MIME” then the superblock containsMultipurpose Internet Mail Extensions (MIME) data according to RFC 2045(Freed, N., and N. Borenstein, “Multipurpose Internet Mail Extensions(MIME)—Part One: Format of Internet Message Bodies”, RFC 2045, November1996), RFC 2046 (Freed, N., and N. Borenstein, “Multipurpose InternetMail Extensions (MIME)—Part Two: Media Types”, RFC 2046, November 1996)and related RFCs. The MIME data consists of a header followed by a body.The header is encoded as a variable-length text string preceded by an8-bit string length. The body is encoded as a variable-lengthtype-specific octet stream preceded by a 16-bit size in big-endianformat.

The basic top-level media types described in RFC 2046 include text,image, audio, video and application.

RFC 2425 (Howes, T., M. Smith and F. Dawson, “A MIME Content-Type forDirectory Information”, RFC 2045, September 1998) and RFC 2426 (Dawson,F., and T. Howes, “vCard MIME Directory Profile”, RFC 2046, September1998) describe a text subtype for directory information suitable, forexample, for encoding contact information which might appear on abusiness card.

Encoding and Printing Considerations

The Print Engine Controller (PEC) (which is the subject of a number ofpending US patent applications, including: Ser. Nos. 09/575,108;10/727,162; 09/575,110; 09/607,985; U.S. Pat. Nos. 6,398,332; 6,394,573;6,622,923) supports the encoding of two fixed (per-page) 2⁴-ary (15,7)Reed-Solomon codewords and four variable (per-tag) 2⁴-ary (15,7)Reed-Solomon codewords, although other numbers of codewords can be usedfor different schemes.

Furthermore, PEC supports the rendering of tags via a rectangular unitcell whose layout is constant (per page) but whose variable codeworddata may vary from one unit cell to the next. PEC does not allow unitcells to overlap in the direction of page movement.

A unit cell compatible with PEC contains a single tag group consistingof four tags. The tag group contains a single A codeword unique to thetag group but replicated four times within the tag group, and fourunique B codewords. These can be encoded using five of PEC's sixsupported variable codewords. The tag group also contains eight fixed Cand D codewords. One of these can be encoded using the remaining one ofPEC's variable codewords, two more can be encoded using PEC's two fixedcodewords, and the remaining five can be encoded and pre-rendered intothe Tag Format Structure (TFS) supplied to PEC.

PEC imposes a limit of 32 unique bit addresses per TFS row. The contentsof the unit cell respect this limit. PEC also imposes a limit of 384 onthe width of the TFS. The contents of the unit cell respect this limit.

Note that for a reasonable page size, the number of variable coordinatebits in the A codeword is modest, making encoding via a lookup tabletractable. Encoding of the B codeword via a lookup table may also bepossible. Note that since a Reed-Solomon code is systematic, only theredundancy data needs to appear in the lookup table.

Imaging and Decoding Considerations

The minimum imaging field of view required to guarantee acquisition ofan entire tag has a diameter of 39.6 s, i.e.(2×(12+2))√{square root over (2)}sallowing for arbitrary alignment between the surface coding and thefield of view. Given a macrodot spacing of 143 μm, this gives a requiredfield of view of 5.7 mm.

Table 4 gives pitch ranges achievable for the present surface coding fordifferent sampling rates, assuming an image sensor size of 128 pixels.

TABLE 4 Pitch ranges achievable for present surface coding for differentsampling rates, computed using Optimize Hyperlabel Optics; dot pitch =1600 dpi, macrodot pitch = 9 dots, viewing distance = 30 mm, nib-to-FOVseparation = 1 mm, image sensor size = 128 pixels sampling rate pitchrange 2 −40 to

49 2.5 −27 to

36 3 −10 to

18

For the surface coding above, the decoding sequence is as follows:

-   -   locate targets of complete tag    -   infer perspective transform from targets    -   sample cyclic position code    -   decode cyclic position code    -   determine orientation from cyclic position code    -   sample and decode local Reed-Solomon codeword    -   determine tag x-y location    -   infer 3D tag transform from oriented targets    -   determine nib x-y location from tag x-y location and 3D        transform    -   determine active area status of nib location with reference to        active area map    -   generate local feedback based on nib active area status    -   determine tag type    -   sample distributed Reed-Solomon codewords (modulo window        alignment, with reference to tag type)    -   decode distributed Reed-Solomon codewords    -   verify tag group data CRC    -   on decode error flag bad region ID sample    -   determine encoding type, and reject unknown encoding    -   determine region flags    -   determine region ID    -   encode region ID, nib x-y location, nib active area status in        digital ink    -   route digital ink based on region flags

Region ID decoding need not occur at the same rate as position decodingand decoding of a codeword can be avoided if the codeword is found to beidentical to an already-known good codeword.

If the high-order coordinate width is non-zero, then special care mustbe taken on boundaries between tags where the low-order x or ycoordinate wraps, otherwise codeword errors may be introduced. Ifwrapping is detected from the low-order x or y coordinate (i.e. itcontains all zero bits or all one bits), then the correspondinghigh-order coordinate can be adjusted before codeword decoding. In theabsence of genuine symbol errors in the high-order coordinate, this willprevent the inadvertent introduction of codeword errors.

Alternative Tag Arrangements

It will be appreciated that a range of different tag layouts and tagstructures can be utilised.

For example, the tag group shown in FIG. 9 can be replaced with the taggroup shown in FIG. 16, in which the tags are not rotated relative toeach other. FIG. 17 shows an arrangement that utilises a six-foldrotational symmetry at the physical level, with each diamond shaperepresenting a respective symbol. FIG. 18 shows a version of the tag inwhich the tag is expanded to increase its data capacity by addingadditional bands of symbols about its circumference.

The use of these alternative tag structures, including associatedencoding considerations, is described shown in more detail in thecopending patent application Ser. Nos. 10/409,864, 10/309,358,10/410,484, and 10/786,631 the contents of which is incorporated hereinby cross reference.

Security Discussion

As described above, authentication relies on verifying thecorrespondence between data and a signature of that data. The greaterthe difficulty in forging a signature, the greater the trustworthinessof signature-based authentication.

The item ID is unique and therefore provides a basis for a signature. Ifonline authentication access is assumed, then the signature may simplybe a random number associated with the item ID in an authenticationdatabase accessible to the trusted online authenticator. The randomnumber may be generated by any suitable method, such as via adeterministic (pseudo-random) algorithm, or via a stochastic physicalprocess. A keyed hash or encrypted hash may be preferable to a randomnumber since it requires no additional space in the authenticationdatabase. However, a random signature of the same length as a keyedsignature is more secure than the keyed signature since it is notsusceptible to key attacks. Equivalently, a shorter random signatureconfers the same security as a longer keyed signature.

In the limit case no signature is actually required, since the merepresence of the item ID in the database indicates authenticity. However,the use of a signature limits a forger to forging items he has actuallysighted.

To prevent forgery of a signature for an unsighted ID, the signaturemust be large enough to make exhaustive search via repeated accesses tothe online authenticator intractable. If the signature is generatedusing a key rather than randomly, then its length must also be largeenough to prevent the forger from deducing the key from knownID-signature pairs. Signatures of a few hundred bits are consideredsecure, whether generated using private or secret keys.

While it may be practical to include a reasonably secure randomsignature in a tag (or local tag group), particularly if the length ofthe ID is reduced to provide more space for the signature, it may beimpractical to include a secure ID-derived signature in a tag. Tosupport a secure ID-derived signature, we can instead distributefragments of the signature across multiple tags. If each fragment can beverified in isolation against the ID, then the goal of supportingauthentication without increasing the sensing device field of view isachieved. The security of the signature can still derive from the fulllength of the signature rather than from the length of a fragment, sincea forger cannot predict which fragment a user will randomly choose toverify. A trusted authenticator can always perform fragment verificationsince they have access to the key and/or the full stored signature, sofragment verification is always possible when online access to a trustedauthenticator is available.

Fragment verification requires that we prevent brute force attacks onindividual fragments, otherwise a forger can determine the entiresignature by attacking each fragment in turn. A brute force attack canbe prevented by throttling the authenticator on a per-ID basis. However,if fragments are short, then extreme throttling is required. As analternative to throttling the authenticator, the authenticator caninstead enforce a limit on the number of verification requests it iswilling to respond to for a given fragment number. Even if the limit ismade quite small, it is unlikely that a normal user will exhaust it fora given fragment, since there will be many fragments available and theactual fragment chosen by the user can vary. Even a limit of one can bepractical. More generally, the limit should be proportional to the sizeof the fragment, i.e. the smaller the fragment the smaller the limit.Thus the experience of the user would be somewhat invariant of fragmentsize. Both throttling and enforcing fragment verification limits implyserialisation of requests to the authenticator. Enforcing fragmentverification limits further requires the authenticator to maintain aper-fragment count of satisfied verification requests.

A brute force attack can also be prevented by concatenating the fragmentwith a random signature encoded in the tag. While the random signaturecan be thought of as protecting the fragment, the fragment can also bethought of as simply increasing the length of the random signature andhence increasing its security.

Fragment verification may be made more secure by requiring theverification of a minimum number of fragments simultaneously.

Fragment verification requires fragment identification. Fragments may beexplicitly numbered, or may more economically be identified by thetwo-dimensional coordinate of their tag, modulo the repetition of thesignature across a continuous tiling of tags.

The limited length of the ID itself introduces a further vulnerability.Ideally it should be at least a few hundred bits. In the Netpage surfacecoding scheme it is 96 bits or less. To overcome this the ID may bepadded. For this to be effective the padding must be variable, i.e. itmust vary from one ID to the next. Ideally the padding is simply arandom number, and must then be stored in the authentication databaseindexed by ID. If the padding is deterministically generated from the IDthen it is worthless.

Offline authentication of secret-key signatures requires the use of atrusted offline authentication device. The QA integrated circuit (whichis the subject of a number of pending US patent applications, includingSer. Nos. 09/112,763; 09/112,762; 09/112,737; 09/112,761; 09/113,223)provides the basis for such a device, although of limited capacity. TheQA integrated circuit can be programmed to verify a signature using asecret key securely held in its internal memory. In this scenario,however, it is impractical to support per-ID padding, and it isimpractical even to support more than a very few secret keys.Furthermore, a QA integrated circuit programmed in this manner issusceptible to a chosen-message attack. These constraints limit theapplicability of a QA-integrated circuit-based trusted offlineauthentication device to niche applications.

In general, despite the claimed security of any particular trustedoffline authentication device, creators of secure items are likely to bereluctant to entrust their secret signature keys to such devices, andthis is again likely to limit the applicability of such devices to nicheapplications.

By contrast, offline authentication of public-key signatures (i.e.generated using the corresponding private keys) is highly practical. Anoffline authentication device utilising public keys can trivially holdany number of public keys, and may be designed to retrieve additionalpublic keys on demand, via a transient online connection, when itencounters an ID for which it knows it has no corresponding publicsignature key. Untrusted offline authentication is likely to beattractive to most creators of secure items, since they are able toretain exclusive control of their private signature keys.

A disadvantage of offline authentication of a public-key signature isthat the entire signature must be acquired from the coding, violatingour desire to support authentication with a minimal field of view. Acorresponding advantage of offline authentication of a public-keysignature is that access to the ID padding is no longer required, sincedecryption of the signature using the public signature key generatesboth the ID and its padding, and the padding can then be ignored. Aforger can not take advantage of the fact that the padding is ignoredduring offline authentication, since the padding is not ignored duringonline authentication.

Acquisition of an entire distributed signature is not particularlyonerous. Any random or linear swipe of a hand-held sensing device acrossa coded surface allows it to quickly acquire all of the fragments of thesignature. The sensing device can easily be programmed to signal theuser when it has acquired a full set of fragments and has completedauthentication. A scanning laser can also easily acquire all of thefragments of the signature. Both kinds of devices may be programmed toonly perform authentication when the tags indicate the presence of asignature.

Note that a public-key signature may be authenticated online via any ofits fragments in the same way as any signature, whether generatedrandomly or using a secret key. The trusted online authenticator maygenerate the signature on demand using the private key and ID padding,or may store the signature explicitly in the authentication database.The latter approach obviates the need to store the ID padding.

Note also that signature-based authentication may be used in place offragment-based authentication even when online access to a trustedauthenticator is available.

Table 5 provides a summary of which signature schemes are workable inlight of the foregoing discussion.

TABLE 5 Summary of workable signature schemes encoding acquisitionsignature online offline in tags from tags generation authenticationauthentication Local full random ok Impractical to store per IDinformation secret key Signature Undesirable to too short to storesecret be secure keys private key Signature too short to be secureDistrib- fragment(s) random ok impractical^(b) uted secret key okimpractical^(c) private key ok impractical^(b) full random okimpractical^(b) secret key ok impractical^(c) private key ok okSecurity Specification

FIG. 19 shows an example item signature object model.

An item has an ID (X) and other details (not shown). It optionally has asecret signature (Z). It also optionally has a public-key signature. Thepublic-key signature records the signature (S) explicitly, and/orrecords the padding (P) used in conjunction with the ID to generate thesignature. The public-key signature has an associated public-private keypair (K, L). The key pair is associated with a one or more ranges ofitem IDs.

Typically issuers of security documents and pharmaceuticals will utilisea range of IDs to identify a range of documents or the like. Followingthis, the issuer will then use these details to generate respective IDsfor each item, or document to be marked.

Authentication of the product can then be performed online or offline bysensing the tag data encoded within the tag, and performing theauthentication using a number of different mechanisms depending on thesituation.

Examples of the processes involved will now be described for public andprivate key encryption respectively.

Authentication Based on Public-Key Signature

Setup Per ID Range:

-   -   generate public-private signature key pair (K, L)    -   store key pair (K, L) indexed by ID range

Setup Per ID:

-   -   generate ID padding (P)    -   retrieve private signature key (L) by ID (X)    -   generate signature (S) by encrypting ID (X) and padding (P)        using private key (L):        -   S←E_(L)(X, P)    -   store signature (S) in database indexed by ID (X) (and/or store        padding (P))    -   encode ID (X) in all tag groups    -   encode signature (S) across multiple tags in repeated fashion

Online Fragment-Based Authentication (User):

-   -   acquire ID (X) from tags    -   acquire position (x, y)_(i) and signature fragment (T_(i)) from        tag    -   generate fragment number (i) from position (x, y)_(i):        -   i←F[(x, y)_(i)]    -   look up trusted authenticator by ID (X)    -   transmit ID (X), fragment (S_(i)) and fragment number (i) to        trusted authenticator

Online Fragment-Based Authentication (Trusted Authenticator):

-   -   receive ID (X), fragment (S_(i)) and fragment number (i) from        user    -   retrieve signature (S) from database by ID (X) (or re-generate        signature)    -   compare received fragment (T_(i)) with corresponding fragment of        signature (S_(i))    -   report authentication result to user

Offline Signature-Based Authentication (User):

-   -   acquire ID from tags (X)    -   acquire positions (x, y)_(i) and signature fragments (T_(i))        from tag    -   generate fragment numbers (i) from positions (x, y)_(i):        -   i←F[(x, y)_(i)]        -   S←S₀|S₁| . . . |S_(n-1)    -   generate signature (S) from (n) fragments:    -   retrieve public signature key (K) by ID (X)    -   decrypt signature (S) using public key (K) to obtain ID (X′) and        padding (P′):        -   X′|P′←D_(K)(S)    -   compare acquired ID (X) with decrypted ID (X′)    -   report authentication result to user        Authentication Based on Secret-Key Signature

Setup Per ID:

-   -   generate secret (Z)    -   store secret (Z) in database indexed by ID (X)    -   encode ID (X) and secret (Z) in all tag groups

Online Secret-Based Authentication (User):

-   -   acquire ID (X) from tags    -   acquire secret (Z′) from tags    -   look up trusted authenticator by ID    -   transmit ID (X) and secret (Z′) to trusted authenticator

Online Secret-Based Authentication (Trusted Authenticator):

-   -   receive ID (X) and secret (Z′) from user    -   retrieve secret (Z) from database by ID (X)    -   compared received secret (Z′) with secret (Z)    -   report authentication result to user

As discussed earlier, secret-based authentication may be used inconjunction with fragment-based authentication.

Cryptographic Algorithms

When the public-key signature is authenticated offline, the user'sauthentication device typically does not have access to the padding usedwhen the signature was originally generated. The signature verificationstep must therefore decrypt the signature to allow the authenticationdevice to compare the ID in the signature with the ID acquired from thetags. This precludes the use of algorithms which don't perform thesignature verification step by decrypting the signature, such as thestandard Digital Signature Algorithm U.S. Department ofCommerce/National Institute of Standards and Technology, DigitalSignature Standard (DSS), FIPS 186-2, 27 Jan. 2000.

RSA encryption is described in:

-   -   Rivest, R. L., A. Shamir, and L. Adleman, “A Method for        Obtaining Digital Signatures and Public-Key Cryptosystems”,        Communications of the ACM, Vol. 21, No. 2, February 1978, pp.        120-126    -   Rivest, R. L., A. Shamir, and L. M. Adleman, “Cryptographic        communications system and method”, U.S. Pat. No. 4,405,829,        issued 20 Sep. 1983    -   RSA Laboratories, PKCS #1 v2.0: RSA Encryption Standard, Oct. 1,        1998

RSA provides a suitable public-key digital signature algorithm thatdecrypts the signature. RSA provides the basis for the ANSI X9.31digital signature standard American National Standards Institute, ANSIX9.31-1998, Digital Signatures Using Reversible Public Key Cryptographyfor the Financial Services Industry (rDSA), Sep. 8, 1998. If no paddingis used, then any public-key signature algorithm can be used.

In the hyperlabel surface coding scheme the ID is 96 bits long or less.It is padded to 160 bits prior to being signed.

The padding is ideally generated using a truly random process, such as aquantum process [14,15], or by distilling randomness from random eventsSchneier, B., Applied Cryptography, Second Edition, John Wiley & Sons1996.

In the hyperlabel surface coding scheme the random signature, or secret,is 36 bits long or less. It is also ideally generated using a trulyrandom process.

Security Tagging and Tracking

Currency, checks and other monetary documents can be tagged in order todetect currency counterfeiting and counter money laundering activities.The Hyperlabel tagged currency can be validated, and tracked through themonetary system. Hyperlabel tagged products such as pharmaceuticals canbe tagged allowing items to be validated and tracked through thedistribution and retail system.

A number of examples of the concepts of Hyperlabel security tagging andtracking referring specifically to bank notes and pharmaceuticals,however Hyperlabel tagging can equally be used to securely tag and trackother products, for example, traveller's checks, demand deposits,passports, chemicals etc.

Hyperlabel tagging, with the Netpage system, provides a mechanism forsecurely validating and tracking objects.

Hyperlabel tags on the surface of an object uniquely identify theobject. Each Hyperlabel tag contains information including the object'sunique ID, and the tag's location on the Hyperlabel tagged surface. AHyperlabel tag also contains a signature fragment which can be used toauthenticate the object. A scanning laser or image sensor can read thetags on any part of the object to identify the object, validate theobject, and allow tracking of the object.

Currency Tagging

An example of the protection of security documents will now be describedwith reference to the specific protection of currency, such as banknotes, although it will be appreciated that the techniques may beapplied to any security document.

Currency may be tagged with Hyperlabels in order to detectcounterfeiting and allow tracking of currency movement. Hyperlabel tagscan be printed over the entire bank note surface or can be printed in asmaller region of the note. Hyperlabel tagging can be used in additionto other security features such as holograms, foil strips,colour-shifting inks etc. A scanning laser or image sensor can read thetags on any part of the note to validate each individual note.

In this example, each hexagonal Hyperlabel currency tag is around 2.5 mmacross, and incorporates a variety of data in the form of printed dotsof infrared ink. An example of a tag included on a bank note is shown inFIG. 20.

A Hyperlabel currency tag identifies the note currency, issue country,and note denomination. It also identifies the note's serial number, thenote side (i.e. front or back), and it may contain other information(for example, the exact printing works where the note was printed).There are two note IDs for each physical bank note—one for each side ofthe note.

The tag may also include:

-   -   Alignment marks (these are the larger dots in the image above)    -   A code indicating that the tag is a currency tag, as opposed to        a commercial Hyperlabel or Hyperlabel tag    -   A horizontal position code, specifying where the tag is along        the note    -   A vertical position code, specifying where the tag is across the        note    -   A cryptographic signature    -   Error detection and correction bits

Each tag is unique. That is, of all tags ever to be printed on any noteor other document, no two valid tags will ever be the same. The tags aredesigned to be easily read with low cost scanners that can be built intoa variety of validation devices.

Hyperlabel currency tags can be read by any Hyperlabel scanner. Thesescanners can be incorporated into a variety of devices to facilitateauthentication and tracking, as will be described in more detail below.

Tracking

For the purpose of tracking and item validation the manufacturer, orother central authority, maintains a database which tracks the locationand status of all currency. This can also be used in authentication ofcurrency.

Each time a note is scanned its location is recorded. This locationinformation can be collected in a central database allowing analysis andidentification of abnormal money movements and detection of counterfeitnotes. This allows the creation of highly accurate intelligence aboutcriminal activity and the real-time detection of the location of stolenor counterfeit notes at many locations within the monetary system. Forexample, in the case of sophisticated forgeries where Hyperlabel dotpatterns are exactly duplicated, there will be multiple copies ofexactly forged notes (at a minimum, the original and the forgery). Ifmultiple identical notes appear in different places at the same time,all but one of the notes must be a forgery. All can then be treated assuspect.

Thus, when a transaction is performed using currency, the generalprocess is as follows:

-   -   a transaction is agreed    -   currency is provided relating to the transaction    -   the currency is scanned using an appropriate sensing device    -   the sensing device sense at least one tag and generates        predetermined data    -   the predetermined data is transferred to a central government        database

In this regard, the following predetermined data is automatically sentfrom the scanners to the central government currency database:

-   -   The serial number of the note    -   The denomination of the note    -   Note validity data    -   The serial number of the scanner    -   The time and date of the scan    -   The physical location of the scanner at the time the scan was        taken (for fixed scanners this is automatic, and for mobile        scanners the physical location is determined using a GPS        tracker)    -   The network location of the scanner    -   The identity of the person making reportable cash transactions

Thus, Hyperlabel technology makes it possible to build databasescontaining the serial number and history of all notes issued, and itallows them to be tracked through the monetary system. The datacollected can be used to build up cash flow maps based on the validationdata received, and its presence will provide a powerful tool for lawenforcement agencies to combat theft, money laundering andcounterfeiting in the global economy.

With each note being tracked over its lifetime, from when it is firstprinted, until it is destroyed. Calculations show that this databasewill need to store in excess of 50 GBytes per day to track all US Dollarmovements. Similar storage is also required for the Euro. This is wellwithin the capabilities of modern database systems.

There are also a large number of transactions involved—several hundredmillion per day. These are within the capability of conventionaldistributed transaction processing systems. However, the Hyperlabelcurrency system can be implemented at substantially lower cost by usingnew generation database systems that perform transactions insemiconductor memory, instead of disk drives. These transactions canthen be continually streamed to disk as a background ‘backup’ task. Suchsystems are likely to be sufficiently mature by the time that aHyperlabel based currency tracking system comes on-line that they willbe a viable choice.

As well as basic tracking and validation functions, the database systemmay have the following additional features:

-   -   Indication of abnormal money movement patterns within the system        (e.g. large cash payments made at different locations within the        system by persons of interest)    -   The provision of cash flow demand forecasts    -   Data mining features that could be used to detect and prosecute        counterfeiters and money launderers    -   Neural network based fraud detection    -   Geographic trends identification

Thus, the central database maintains up-to-date information on validobject IDs, an object ID hotlist (for all suspect object IDs), and alist of public keys corresponding to object IDs. The central server alsomaintains an object scanning history to track an object's movements.Each time an object is scanned, its timestamped location is recorded. Ifknown, the details of the object owner may also be recorded. Thisinformation may be known particularly in the case of large financialtransactions e.g. a large cash withdrawal from a bank. This objectscanning history data can be used to detect illegal product movements,for example, the illegal import of currency. It can also be used todetect abnormal or suspicious product movements which may be indicativeof product counterfeiting.

If an object is known to be stolen it can be immediately added to anobject ID hotlist on the central server. This hotlist is automaticallydistributed to (or becomes accessible to) all on-line scanners, and willbe downloaded to all off-line scanners on their next update. In this waythe stolen status is automatically and rapidly disseminated to a hugenumber of outlets. Similarly, if an object is in any other way suspectit can be added to the hotlist so that its status is flagged to theperson scanning the object.

An on-line scanner has instant access to the central server to allowchecking of each object ID at the time of scanning. The object scanninghistory is also updated at the central server at the time the object isscanned.

An off-line scanner stores object status data internally to allowvalidation of a scanned object. The object status data includes valid IDrange lists, an object ID hotlist, a public key list, and an objectscanning history. Each time an object is scanned the details arerecorded in the object scanning history. The object status data isdownloaded from the central server, and the object scanning history isuploaded to the central server, each time the scanner connects.

A mobile scanner's location can be provided to the application by thescanner, if it is GPS-equipped. Alternatively the scanner's location canbe provided by the network through which it communicates.

For example, if the hand-held scanner uses the mobile phone network, thescanner's location can be provided by the mobile phone network provider.There are a number of location technologies available. One is AssistedGlobal Positioning System (A-GPS). This requires a GPS-equipped handset,which receives positioning signals from GPS satellites. The phonenetwork knows the approximate location of the handset (in this case thehandset is also the scanner) from the nearest cell site. Based on this,the network tells the handset which GPS satellites to use in itsposition calculations. Another technology, which does not require thedevice to be GPS-equipped, is Uplink Time Difference of Arrival(U-TDOA). This determines the location of a wireless handset, using aform of triangulation, by comparing the time it takes a wirelesshandset's signal to reach several Location Measurement Units (LMUs)installed at the network's cell sites. The handset location is thencalculated based on the differences in arrival times of the three (ormore) signals.

Authentication

Each object ID has a signature. Limited space within the Hyperlabel tagstructure makes it impractical to include a full cryptographic signaturein a tag so signature fragments are distributed across multiple tags. Asmaller random signature, or secret, can be included in a tag.

To avoid any vulnerability due to the limited length of the object ID,the object ID is padded, ideally with a random number. The padding isstored in an authentication database indexed by object ID. Theauthentication database may be managed by the manufacturer, or it may bemanaged by a third-party trusted authenticator.

Each Hyperlabel tag contains a signature fragment and each fragment (ora subset of fragments) can be verified, in isolation, against the objectID. The security of the signature still derives from the full length ofthe signature rather than from the length of the fragment, since aforger cannot predict which fragment a user will randomly choose toverify.

Fragment verification requires fragment identification. Fragments may beexplicitly numbered, or may by identified by the two-dimensionalcoordinate of their tag, modulo the repetition of the signature acrosscontinuous tiling of tags.

Note that a trusted authenticator can always perform fragmentverification, so fragment verification is always possible when on-lineaccess to a trusted authenticator is available.

Establishing Authentication Database

Prior to allocating a new range of IDs, some setup tasks are required toestablish the authentication database.

For each range of IDs a public-private signature key pair is generatedand the key pair is stored in the authentication database, indexed by IDrange.

For each object ID in the range the following setup is required:

-   -   generate ID padding and store in authentication database,        indexed by object ID    -   retrieve private signature key by object ID    -   generate signature by encrypting object ID and padding, using        private key    -   store signature in authentication database indexed by object ID,        and/or store the padding, since the signature can be        re-generated using the ID, padding and private key    -   encode the signature across multiple tags in repeated fashion

This data is required for the Hyperlabel tags therefore theauthentication database must be established prior to, or at the time of,printing of the Hyperlabels.

Security issues are discussed in more detail above.

FIG. 21 summarises note printing and distribution of notes withHyperlabel tags. Notes are also logged in the database whenever they arescanned in circulation, and also when they are destroyed.

While the technology to print commercial Hyperlabel tags will becommercially available, only the authorized currency printing bureaus ofa government will be able to print the codes corresponding to thatgovernment's currency. These codes are protected by 2048 bit RSAcryptography embedded within the integrated circuits (integratedcircuits) embedded in the Memjet™ printers used to print Hyperlabeltags. This is a highly secure form of asymmetric cryptography, usingprivate and public keys. The private keys relating to any particularcurrency would be kept only by authorised national security agencies.

Off-Line Public-Key-Based Authentication

An off-line authentication device utilises public-key signatures. Theauthentication device holds a number of public keys. The device may,optionally, retrieve additional public keys on demand, via a transienton-line connection when it encounters an object ID for which it has nocorresponding public key signature.

For off-line authentication, the entire signature is needed. Theauthentication device is swiped over the Hyperlabel tagged surface and anumber of tags are read. From this, the object ID is acquired, as wellas a number of signature fragments and their positions. The signature isthen generated from these signature fragments. The public key is lookedup, from the scanning device using the object ID. The signature is thendecrypted using the public key, to give an object ID and padding. If theobject ID obtained from the signature matches the object ID in theHyperlabel tag then the object is considered authentic.

The off-line authentication method can also be used on-line, with thetrusted authenticator playing the role of authenticator.

On-Line Public-Key-Based Authentication

An on-line authentication device uses a trusted authenticator to verifythe authenticity of an object. For on-line authentication a single tagcan be all that is required to perform authentication. Theauthentication device scans the object and acquires one or more tags.From this, the object ID is acquired, as well as at least one signaturefragment and its position. The fragment number is generated from thefragment position. The appropriate trusted authenticator is looked up bythe object ID. The object ID, signature fragment, and fragment numberare sent to the trusted authenticator.

The trusted authenticator receives the data and retrieves the signaturefrom the authentication database by object ID. This signature iscompared with the supplied fragment, and the authentication result isreported to the user.

On-Line Secret-Based Authentication

Alternatively or additionally, if a random signature or secret isincluded in each tag (or tag group), then this can be verified withreference to a copy of the secret accessible to a trusted authenticator.Database setup then includes allocating a secret for each object, andstoring it in the authentication database, indexed by object ID.

The authentication device scans the object and acquires one or moretags. From this, the object ID is acquired, as well as the secret. Theappropriate trusted authenticator is looked up by the object ID. Theobject ID and secret are sent to the trusted authenticator.

The trusted authenticator receives the data and retrieves the secretfrom the authentication database by object ID. This secret is comparedwith the supplied secret, and the authentication result is reported tothe user.

Secret-based authentication can be used in conjunction with on-linefragment-based authentication is discussed in more detail above.

Product Scanning Interactions

Product Scanning at a retailer is illustrated in FIG. 22. When a storeoperator scans a Hyperlabel tagged product the tag data is sent to theservice terminal (A). The service terminal sends the transaction data tothe store server (B). The store server sends this data, along with theretailer details, to the manufacturer server (C). The Hyperlabel serverknows which manufacturer server to send the message to from the objectID. On receipt of the input, the manufacturer server authenticates theobject, if the manufacturer is the trusted authenticator. Alternativelythe manufacturer server passes the data on to the authentication serverto verify the object ID and signature (D). The authentication serversends the authentication result back to the manufacturer server (E). Themanufacturer server checks the status of the object ID (against itsvalid ID lists and hotlist), and sends the response to the store server(F), which in turn send the result back the store service terminal (G).The store server could also communicate with the relevant authenticationserver directly.

The interaction detail for on-line product scanning at a retailer isshown in FIG. 23. The store operator scans the Hyperlabel taggedproduct. The scanner sends the scanner ID and tag data to the serviceterminal. The service terminal sends this data along with the terminalID and scanner location to the store server. The store server then sendsthe request on to the manufacturer server, which performs authentication(either itself or via a third party authentication server) anddetermines the object status. The response is then sent back to thestore server, and on to the operator service terminal

The interaction detail for off-line product scanning at a retailer isshown in FIG. 24. The store operator scans the Hyperlabel taggedproduct. The scanner sends the scanner ID and tag data from multipletags to the service terminal. The service terminal sends this data,along with the terminal ID and scanner location, to the store server.The store server then performs off-line authentication, as described inSection 3.4.2, and determines the object status through its cachedhotlist, valid object ID lists, and public key list. The store serverrecords the scan details in its internal object scanning history. Theresponse is then sent back to the operator service terminal

An alternative for off-line product scanner occurs where the scanner isa hand-held, stand-alone scanner. In this case the cached authenticationdata is stored within the scanner itself, and the scanner performs thevalidation internally. The object scanning history is also cached withinthe scanner. Periodically the scanner connects to the central database,uploads it's object scanning history, and downloads the latest publickey list, object ID hotlist and valid ID range list. This connection maybe automatic (and invisible to the user), or may be initiated by theuser, for example, when the scanner is placed in a dockingstation/charger.

Product scanning with a Netpage pen is illustrated in FIG. 25. When auser scans a Hyperlabel tagged item with their Netpage pen, the input issent to the Netpage System, from the user's Netpage pen, in the usualway (A). To scan a product rather than interact with it, the pen can beplaced in a special mode. This is typically a one-shot mode, and can beinitiated by tapping on a <scan> button printed on a Netpage.Alternatively, the pen can have a user-operable button, which, when helddown during a tap or swipe, tells the pen to treat the interaction as aproduct scan rather than a normal interaction. The tag data istransmitted from the pen to the user's Netpage base station. The Netpagebase station may be the user's mobile phone or PDA, or it may be someother Netpage device, such as a PC. The input is relayed to theHyperlabel server (B) and then on to manufacturer server (C) in theusual way. On receipt of the input, the manufacturer serverauthenticates the object if the manufacturer is the trustedauthenticator. Alternatively the manufacturer server passes the data onto the authentication server to verify the object ID and signature (D).The authentication server sends the authentication result back to themanufacturer server (E). The manufacturer server checks the status ofthe object ID (against its valid ID lists and hotlist), and sends theresponse to the Hyperlabel server (G). The Hyperlabel server, as part ofthe Netpage system, can know the identity and devices of the user. TheHyperlabel server will relay the manufacturer server's response to theuser's phone (G) or Web browsing device (H) as appropriate. If theuser's Netpage pen has LEDs then the Hyperlabel server can send acommand to the user's pen to light the appropriate LED(s) (I,J).

The interaction detail for scanning with a Netpage pen is shown in FIG.26. The Netpage pen clicks on the Hyperlabel tagged product. The Netpagepen sends the pen id, the product's tag data and the pen's location tothe Hyperlabel server. If the pen ID is not already associated with ascanner, the Hyperlabel server may create a new scanner record for thepen, or may use the pen ID as a scanner ID. The Hyperlabel server sendsthe scanner ID, tag data, and scanner location (if known) to themanufacturer server, which performs authentication (either itself or viaa third party authentication server) and determines the object status.The response is then sent back to the Hyperlabel server, and on to theuser's default Web browsing device.

Security Tagging and Tracking Object Model

The Security Tagging and Tracking object model revolves aroundHyperlabel tags, object IDs, and signatures. FIG. 36 illustrates themanagement and organisation of these objects.

As shown in FIG. 27, a Hyperlabel tag comprises a tag type, object ID,two-dimensional position and a signature fragment. The tag typeindicates whether this is a tag on a common object, or whether the tagis on a special type of object such as a currency note or apharmaceutical product. A signature fragment has an optional fragmentnumber which identifies the fragment's place within the full signature.

Currency notes are identified by a note ID. The note ID comprises notedata and a serial number. The note data identifies the type of currency,the country of issue, the note denomination, the note side (front orback) and other currency-specific information. There are two note IDsfor each physical bank note—one for each side of the printed note. TheNote ID class diagram is shown in FIG. 28.

Object Description, ownership and aggregation class diagram is shown inFIG. 29. This is described in more detail above.

The Object Scanning History class diagram is shown in FIG. 30. An objecthas an object scanning history, recording each time the scanner scans anobject. Each object scanned event comprises the scanner ID, the date andtime of the scan, and the object status at the time of the scan, and thelocation of the scanner at the time the object was scanned. The objectstatus may be valid, stolen, counterfeit suspected, etc. If known, theobject owner details may also be recorded.

A scanner has a unique scanner ID, a network address, owner informationand a status (e.g. on-line, off-line). A scanner is either a mobilescanner, whose location may vary, or a fixed scanner, whose location isknown and constant. A scanner has a current location, comprising thelocation details and a timestamp. A scanner may be a Netpage pen, inwhich case it will be associated with a Netpage Pen record. If a scannerin off-line, it will keep an object scanning history, and willoptionally store a public key list, a valid ID range list and an objectID hotlist. The scanner class diagram is shown in FIG. 31.

The manufacturer, or other central authority, maintains a number ofObject ID Hot Lists, each with a unique list ID, and the time the listwas last updated. Each hot list comprises a list of suspect object IDs,comprising the object ID, date, time, status (suspected counterfeit,stolen, etc.) and other information. The Object ID Hot List classdiagram is shown in FIG. 32.

The manufacturer, or other central authority, maintains a list of validID ranges. Each valid object ID range entry in the list comprises thestart object ID and end object ID (the valid ID range) and the time theentry was updated. The Valid ID Range List class diagram is shown inFIG. 33.

The manufacturer, or other central authority, maintains a public keylist. The public key list consists of a number of entries identifyingthe public key for a range of Object IDs. Each valid object ID rangeentry comprises the update time for the entry, the start object ID forthe range, the end object ID for the range, and the public keyapplicable to each object ID in the given range. The Public Key Listclass diagram is shown in FIG. 34.

Object authentication may be performed by the manufacturer, or by athird-party trusted authenticator. A trusted authenticator has anauthenticator ID, name and details. A trusted authenticator holds a listof public-private key pairs, each associated with one or more ID ranges.This is a list of object ID ranges (identified by the start and end ID)and the corresponding public/private signature key pair. A trustedauthenticator also holds a list of secret signatures, and a list ofpublic-key signatures. Each public-key signature identifies the actualsignature and/or the padding used to generate the signature. Each secretsignature and public-key signature is associated by object ID with aunique object. The Trusted Authenticator class diagram is shown in FIG.35.

Security Document Scanners

Hyperlabel scanners can be built into a variety of devices. Scanners maybe fixed or mobile. A fixed scanner has a permanent, known location. Amobile scanner has no fixed location. A scanner may be on-line, i.e.have immediate access to the central database, or it may be off-line.

Hyperlabel scanners can determine both the validity and the value ofcurrency. Their determination of a note's validity is more definite andmore secure than current methods, and can be implemented at lower cost.

Scanners may be specific to a particular product application, such as acurrency counter, or may be a generic Hyperlabel scanner. Hyperlabelscanners may be embedded in other multi-function devices, for example, amobile phone or PDA. Such scanners are multi-purpose since they can alsobe used to scan Hyperlabel tagged consumer goods and printed materials.A small hand-held scanner may also be used to scan and validatecurrency. When a scanner scans a note it notifies the currency server ofthe note details, the current date and time, and the scanner location(if known). Optionally the scanner may also send the identity of theperson making the cash transaction, if known. This information would beavailable in respect of bank transactions, currency exchanges and largecash transactions.

Accordingly, hyperlabel currency tags can be read using many types ofdevice, including:

-   -   Currency counters    -   Automated teller machines    -   Cash registers    -   POS checkouts    -   Mobile phone with inbuilt scanner    -   Hyperlabel pens    -   Vending machines

The Hyperlabel technology used in these devices can be implemented in awide range of applications. As a result, the development and deploymentcosts can be shared by the key stakeholders. Of the seven types ofscanner listed, only the currency counters and vending machines arespecific to currency. The other five are also used for scanning consumergoods and printed materials.

Hyperlabel scanners built into a variety of products will include thefollowing features, currently under development at Silverbrook Research.

-   -   An infrared image sensor to read the Hyperlabel tags that        uniquely identify each note.    -   A 32 bit RISC processor with 20 megabits of secure code space        signed using 2048 bit RSA cryptography.    -   A highly secure processor with cryptographic and physical        security features for verifying the cryptographic signature on        Hyperlabel tags (under development at Silverbrook Research).    -   Infrared optics, including filters tuned to the Hyperlabel ink        infrared spectrum.    -   A real-time clock to verify the time of each transaction        reported.    -   Software to decode the Hyperlabel tags, record the details of        each scan, to validate each note scanned, and to facilitate        automatic and secure communications with an online database.    -   Communications systems to create secure network connections to        the central currency verification database.

Various of the Hyperlabel scanners described below are also planned toinclude the following units:

-   -   An inbuilt display and data entry mechanism to indicate to the        operator the amount of money counted, notes that are suspected        of being counterfeit, and the identity of the person requesting        reportable cash transactions.    -   A cache of the serial numbers of all known counterfeit and        stolen notes.    -   Other spectral filters tuned to the secure currency ink spectrum        (which differs from the commercially available Hyperlabel ink).    -   A GPS tracker to verify the location of the currency counter at        the time of use.        Currency Counters

A Hyperlabel currency counter with an inbuilt infrared scanner can beused to automatically scan, validate, and log each note in the centralcurrency database as it is counted. An example of the implementation ofthis is shown in FIG. 37.

These units could replace existing currency counting machines now in usein banks, in foreign exchange offices, in bill payment agenciesaccepting cash payments, and in immigration offices at internationalairports.

As a currency scanner has no other obvious application other thancurrency. It does not need to communicate with any database other thanthe government currency database. A currency scanner may operate at highspeed, requiring excess dataline bandwidth and transaction processing.To overcome this, the banknote validity data can be locally cached, andupdated whenever it changes. Information on scanned notes is sentperiodically in an encrypted form. Although the banknote locationupdates may be sent periodically security and timeliness for detectionare not compromised. This is because data on any counterfeit or stolennotes could be sent immediately. The time of the scan is locallydetermined and accurately included in the data packet, and the list ofcounterfeit and stolen notes is updated as soon as the information isavailable.

Automated Teller Machines

An Automatic Teller Machine (ATM) is a relatively simple case, as it istypically not used for depositing cash, only dispensing it. Accordingly,they are not required to validate the notes. Notes can be validated andlogged using a currency counter when they are placed into the ATM.

ATMs can be equipped with Hyperlabel scanners, which register notes asthey are loaded into, as well as taken out of, the ATM. As well asproviding currency tracking features, this will also reduce theft of,and from, ATMs. This is because the money taken from the ATM will betracked, and as soon as the theft is reported, the money will berecorded in the central database as stolen.

Thus, as shown in FIG. 38, the ATM can track the details of the accountfrom which the funds were withdrawn. This allows the particular notesdispensed to be logged as stolen if the real account holder notifies thebank of fraudulent transactions involving lost or stolen cards.

Cash Registers

Cash registers can have an add-on or built-in currency scanner for asmall additional cost per unit. The notes are scanned as they are putinto, or taken out of, the cash drawer. This also aids verification thatthe correct amount of money has been tendered, and the correct changegiven.

Tracking currency in and out of cash registers can enhance the safety ofshop attendants. Once criminals become aware that stolen cash will beimmediately recorded as stolen, then the incidence of theft should besignificantly reduced.

As shown in FIG. 39, this is typically achieved by having the cashregister communicate with a secure currency server, via a Hyperlabelserver and a local shop database. Thus, the cash register can transferinformation regarding transactions to the local database, whichdetermines if local verification is sufficient, or if global validationor the like is required. Thus, for example, offline authentication maybe used for transactions below a certain threshold required for

In this latter case, a request for verification or the like can berouted to the Hyperlabel server, which will then determine an associatedsecure currency, and route the request accordingly, allowing the securecurrency server to perform authentication using the online

Hyperlabel Supermarket Checkout

One of the major applications of Hyperlabel is in consumer packagedgoods, where it has the potential of being the ‘next generation barcode’ allowing automatic tracking of individual grocery items. Thisapplication requires automatic supermarket checkouts that scan productsfor Hyperlabels. These checkouts will be able to read currencyHyperlabel tags. This allows the currency to be tracked, but alsosimplifies payment, as the amount of money tendered is simply determinedby passing it through the Hyperlabel scan field.

An example of a hyperlabel supermarket checkout is shown in FIG. 40,with examples being described in more detail in applicant's copendingapplications, the contents of which is incorporated herein by crossreference.

Mobile Phone with Inbuilt Scanner

A mobile phone that has an inbuilt infrared scanner to scan and validateeach note can be used in a range of locations where money counting isnot a normal function. It is also used for other inventory managementand validity checking applications, such as pharmaceutical security,forensic investigations, policing trademark infringement, andstocktaking, and is intended for wide distribution.

Tracking currency in and out of cash registers can enhance the safety ofshop attendants as criminal activity should be affected by therealization that all notes taken from a cash register will beimmediately registered as stolen, and that the criminal will run therisk of being caught just by using that cash in everyday transactions orby holding the cash.

Handheld Validity Scanner

Handheld Hyperlabel validity scanners may also be used where currencycounters are not required or suitable. These devices are expected to besignificantly more common than currency counters, as they have multipleuses, and will be much cheaper. An example of a handheld validityscanner is shown in FIG. 41, and described in more detail in applicant'scopending applications, the contents of which is incorporated herein bycross reference.

An example of communications used in implementing a second example of ahandheld scanner is shown in FIG. 42.

The validity scanner has multiple uses, including pharmaceuticalsecurity, brand-name security, stocktaking, forensic investigations, andpolicing. As it is not a dedicated currency device. It does notcommunicate directly with the government currency server as otherwise,large numbers of non-currency related messages would need to be routedthrough that server. Instead, it communicates directly with commercialHyperlabel servers, and any currency related validation requests arepassed on to the government server. To reduce the transaction load onthe government server, note related information can be cached at theHyperlabel server, much as they are cached in the currency counters.

The link to the database would typically be relayed over a radio link toallow local mobility. The radio link can be WiFi, GPRS, 3G mobile,Bluetooth, or other IP link, as appropriate. Internet transactions aresecured using encrypted packets.

Hyperlabel Pen

The Hyperlabel pen is a miniature low cost scanner for consumer andbusiness use. It uses an infrared image sensor, instead of a laserscanner, and scans a Hyperlabel tag whenever it is clicked against asurface.

Details of Hyperlabel pens are described for example in applicant'scopending patent applications, the contents of which are incorporatedherein by cross reference.

These pens are intended for high volume consumer use, with intendeddistribution exceeding 100 million units. While its primary applicationis a wide range of ‘interactive paper’ and computer peripheral uses, italso allows consumers to verify Hyperlabel tags printed on currency,pharmaceuticals, and other objects. The Hyperlabel network will bemanaged by dedicated Hyperlabel servers, and any currency scans fromHyperlabel pens will be routed through these servers to a single logicalconnection to the Currency Servers. Because the costs are borneelsewhere, a huge number of currency validation and logging points canbe added to the network at negligible incremental cost.

The pens do not have a display device, and are intended to be used inconjunction with a device with a display capability and a networkconnection, as shown in FIG. 43. As validation is a secondary functionof the pens, they do not communicate directly with the currencydatabase, and instead transfer requests via a relay device. Only a smallfraction of pen hits (much less than 1%) are expected to be related tocurrency validation. The pens communicate by radio (typically Bluetooth)to the relay, which may be a computer, a mobile phone, a printer, orother computing device.

This relay device communicates, in turn, with the Hyperlabel server. Ifthe Hyperlabel server determines that the pen has clicked on a currencytag, the click is interpreted as a validation query, which is thenforwarded to the appropriate currency server. The currency server logsthe identity and the network location of the pen that clicked on thenote, as well as other data such as the note serial number, the time andthe date. The physical location of the pen is typically unknown, asHyperlabel pens usually do not include a GPS tracker. The currencyserver passes the validation message back to the Hyperlabel server,which formats the message for the display device that relayed themessage from the pen.

Vending Machine

For a small additional cost, Hyperlabel scanners can also be added tovending machines to securely determine both the validity and the valueof a note, as shown in FIG. 44. They also reduce the risk of currencytheft from the vending machine. Vending machines are somewhatcomplimentary to ATMs—they accept notes, but do not dispense them.

Hyperlabel scanners send data to a remote secure server for storage andinterpretation. A direct wireless or wired link can be establishedbetween the server and a scanner for communication. Alternatively, thescanners can communicate with the secure server indirectly through acompanion device such as a point of sale (POS) terminal, a mobile phone,or computer. The database can be updated by scanners operating online inreal-time, or periodically using batch file downloads. High speedscanners can cache lists of counterfeit and stolen notes locally, toreduce network traffic.

The validation messages can go directly to the currency server, or viathe server of the company which owns and operates the vending machine.The vending machine can be configured to automatically reject any stolenor counterfeit notes. It is possible to display the status of the note(i.e. stolen or counterfeit) on most vending machines, and it ispossible that this would act as a further crime deterrent—for even ahumble vending machine can conspicuously identify dubious currency. Itshould only report this when the certainty is 100%. On lowercertainties, it can simply reject the note without stating why, as isthe current practice for vending machines.

Security Features

Hyperlabel currency security features include:

-   -   Notes can be tracked whenever they are scanned—at banks,        supermarket checkouts, vending machines, cash registers, and low        cost home scanners.    -   The unique range of currency tag numbers can be printed only by        the government printing agency.    -   Currency IR ink with unique spectral properties, can be made        available only to government printing agencies.    -   Note serial number printed in tag must match printed serial        number.    -   Tags are printed all over both sides of the note.    -   Tags vary across the note—a forger must match the thousands of        tags printed on any note.    -   Additional proprietary security features not disclosed in this        document.    -   The ability to determine both the validity and the value of        currency.        Security Requirements

For a low risk currency anti-forgery system, it is only necessary tomake it uneconomic. That is, all that is required is that the cost offorging a note exceeds the face value of the note, taking intoconsideration likely advances in technology. A good system should alsomake it easy to detect and track counterfeiters and money launderers.The Hyperlabel system offers a practical solution that meets theseobjectives.

Table 6 outlines various levels of counterfeiting skill, and thecorresponding ability of the Hyperlabel system to detect counterfeitcurrency.

TABLE 6 Scanner reports Counterfeit Counterfeiter probability of levelcharacteristic Note characteristic counterfeit Photocopy Casual forgerNo Hyperlabel tags 100% certainty Hyperlabel Home forger, usingHyperlabel tags are 100% certainty printer computers and printerspresent, but they are not valid currency codes. Sophisticated - Skilfulforger who creates Tag serial number 100% certainty computer a computersystem to does not match systems generate a sequence of cryptographicexpert Hyperlabel tags signature in tag Sophisticated No access tospecial ink Hyperlabel currency 100% certainty using tags printed withcurrency counters. commercial Some scanner types Hyperlabel IR ink (e.g.Hyperlabel instead of secure pens) do not detect currency IR ink thespecial ink High level Highly skilled forger who Hyperlabel tags do 100%certainty forgery copies a tag from a note, not vary correctly andreplicates it across over the note the note using illegally obtainedsecure IR ink Perfect Conventional, highly 100,000 copies of an 99.999%certainty on forgery skilled forger who existing note that are any note,as the meticulously copies every perfect in all respects, 100,000forgeries dot on the whole note, including ink and all- cannot be andprints them with over pattern of valid distinguished from illegallyobtained secure tags. All 100,000 the original valid IR ink notes havethe same note. The forgeries serial number are easily detected by humansdue to repeating serial numbers. Perfect Conventional, highly 100,000copies of an 100% certainty (with forgery (with skilled forger whoexisting note that are aid of operator different perfectly copies everydot perfect in all respects, verification of printed serial on the wholenote, then but 100,000 notes all serial number) numbers) ensures thatthe printed have different serial serial numbers increment. numbersLarge scale A massive effort, where No more than one 50% certainty onany effort many notes are collected, copy of any existing one note - asthe (uneconomic) and each note is note is printed, but single forgerycannot individually analysed and that copy is perfect in bedistinguished from duplicated. all respects. The the original. forgersanalyse and However, a pattern of copy one note at a duplications wouldtime. be evident if more than one forged note was passed at a time.Benefits of a Hyperlabel Security Document SystemTheft

Hyperlabel scanners report the locations of banknotes to a centralsecure database. Repositories of cash—banks, ATMs, cash registers,armored trucks, personal safes—that are equipped with Hyperlabelscanners have records of all of the serial numbers of the notes thatshould be in the repository. Whenever cash is stolen from such arepository, the central database operator can be notified, and the notescarrying the serial numbers will rapidly be registered as stolen. As therecords are kept in a remote secure location (i.e. the centraldatabase), the records will not be stolen along with the cash.

The stolen status is rapidly and automatically disseminated to a hugenumber of outlets as varied as financial institutions and retailers.Each of those outlets will be able to rapidly, accurately andautomatically identify stolen notes as part of their standardcash-handling procedures.

The stolen status is also rapidly and automatically disseminated torelevant agencies such as Customs, Immigration and Police, Hence lawenforcement officers will be armed with mobile scanners that canaccurately and immediately ascertain the status of suspect notes.

Once the stolen cash is used anywhere there is a Hyperlabel scanner, thecash will be identified as stolen. This places the thief in high dangerof being caught. It would thus be very difficult for a thief to disposeof any significant amount of stolen cash.

Hyperlabel scanners can assist in the reduction of theft in manysituations, including:

-   -   Bank and armored truck robbery: all notes would be immediately        ‘marked as stolen’ as soon as the thieves left the scene of the        crime.    -   Retail shops: late night shops, such as 7-eleven and gas        stations—are notoriously victims of small scale armed and        unarmed robberies. The reduction of this kind of theft should        make these occupations substantially safer.    -   For similar reasons, ATMs, personal and company safes, vending        machines, would all become significantly more secure.        Drug Dealing

Indirectly, this could also limit the activities of drug dealers. At thestreet level, many notes used to pay for drugs may be registered asstolen. As the number of these stolen notes accumulates, the cash flowpattern will be identified as suspicious. Therefore, drug dealers wouldwant to be able to verify that any money paid to them was not stolen orcounterfeit.

Ironically, drug dealers will not be able to use Hyperlabel scanners toverify the status of cash they are paid with, without also running therisk of being caught. If a drug dealer was frequently verifying largeamounts of cash, where a large percentage of that cash was stolen, theycould be investigated for money laundering.

Counterfeiting

As well as assisting in the apprehension of criminals, the collection ofthis data also allows the detection of sophisticated forgeries where theHyperlabel dot patterns are exactly duplicated. This is because therewill be multiple copies of exactly forged notes—at least the originaland the forgery. For example, if multiple identical notes appear indifferent places at the same time, all but one of those notes must be aforgery. This applies even if the note is an absolutely perfect forgery,as no two Hyperlabel tags should ever be the same. An heuristicdetermines whether the appearance of a particular note in differentplaces in quick succession is feasible. If successive appearances of anote are determined to be infeasible, the presence of a forgery isindicated.

Money Counting

Because the hyperlabel tags encode the denomination of currency, thisallows money to be counted solely on the basis of hyperlabel detection.This avoids the need for the detection and interpretation of a visiblenumeral, which typically requires complex image processing to beperformed, especially if the quality of the note is degraded due toextensive use.

It will be appreciated that in addition to this, as the denomination isrepeated substantially over the entire currency, this ensures that thecurrency value can be determined even if a large portion of the note isdamaged.

Money Laundering

As discussed in the background, there are two claim stages in moneylaundering, namely placement and wiring and integration.

It will be appreciated that by providing for tracking of each individualnote utilising the Hyperlabel system described above, this makes itextremely difficult for placement to be carried out, primarily as eachindividual note can be tracked throughout its life. Accordingly, largeamounts of currency suddenly entering into the circulation will beeasily detectable primarily as there will be a break in the history ofthe note.

Thus, the system can utilise Patent detection algorithms to identifywhen large volumes of currency either exit or enter into circulationthereby identifying potential sources of money laundering. In additionto this however currency in which has a certain times been owned bycertain individuals can also be tracked. This allows Patents within anindividual's accounts usage to be determined which also helps identifymoney laundering.

Meeting Regulatory Requirements

It will be appreciated that by providing a database which can be used totrack all currency, this allows banks to ensure regulatory requirementsare satisfied. To even further aid with this, rules can be defined whichrepresent the regulatory requirements. In this instance, when atransaction is to be performed, the transaction can be compared to thepredetermined rules to determine if the transaction is allowable. Thiswill effectively prevent unallowable transactions occurring therebyensuring that the banks meet the regulatory requirements.

Cross Boarder Controls

In order to provide for cross boarder control, it is merely necessary tocontinuously monitor the location of currency documents. If currencydocuments on subsequent transactions are provided in different locationsthis indicates that the currency has been physically moved therebyallowing cross boarder currency movements to be determined

Security Document Transfer

It will be appreciated that as the security document can be representedwholly electronically, by use of the identity and correspondencesignature, it is possible to electronically transfer security documents.In this instance, specialised transfer machines can be provided whichoperate to destroy a currency document upon receipt. The document can beconverted to an electronic form by identifying the correspondingdocument layout and tag map used to place the coded data thereon. Thisinformation can then be transferred to a corresponding machine inanother location allowing the security document to be reproduced. Thus,the security document may transferred to one location to anotherlocation in an electronic form by ensuring that only one securitydocument is produced this prevents document duplication whilst allowingsecure transfer.

Advantages of a Hyperlabel Security Document System

The proposed Hyperlabel solution can be implemented to bring manyadvantages. Some of these include:

-   -   Unobtrusive to the public    -   Follows existing cash handling processes    -   Reduces reliance on paper trails    -   Provides a strong deterrent for accepting counterfeit currency    -   Provides a strong deterrent for laundering large amounts of cash    -   Efficient way to share resources across national and        international agencies    -   Improves confidence in the financial system    -   Limits the possibility of inexplicable changes in money demand    -   Reduces risk to integrity of financial institutions    -   Helps banks implement and automate due diligence methods for        cash transactions

There are several major advantages of Hyperlabel currency tags overother existing forms of note validation such as RFID, including:

-   -   Hyperlabel tags are invisible, so they do not affect note design        or graphics.    -   Hyperlabel tags can be implemented at very low cost—the tags are        just ink and are printed while the notes are still in roll form,        directly after the visible inks are printed.    -   Hyperlabel tagged currency is extremely difficult to forge.    -   Hyperlabel tags are printed over the entire note surface in a        highly redundant and fault tolerant manner.    -   Hyperlabel tags are very unlikely to become unreadable due to        note damage.    -   Hyperlabel tags can be scanned using a variety of scanners.    -   Currency location and reportable cash transaction data are        automatically collected.

Hyperlabels support omnidirectional reading, they can protect privacy,they can be produced for a low cost, and the ability of the scanners toread the tags is independent of packaging, contents, or environmentalconditions.

One of the most effective methods to reduce the counterfeit risksconsidered above, is the introduction of a new form of currencyincorporating a machine readable code, and the means to validate notesat key points where cash transactions occur. Counterfeit notes couldthen be detected at banks, currency exchanges, airports, retailers andbill payment service providers accepting cash payments. That is, thegoal would be to identify and reject counterfeit notes before they enterthe monetary system.

Counterfeit notes can vary in quality—depending on the level of skill ofthe counterfeiter and the choice of technology. Hyperlabel providessecurity against the full range of efforts—from casual forgery on acolor photocopier, through to multi-million dollar efforts byprofessional criminals.

By implementing a Hyperlabel system, it becomes possible to monitor andforecast national and international cash flow changes, as well asprovide alerts for any abnormal patterns that could lead to unwantedmacroeconomic outcomes.

An automated Hyperlabel system aids with the record keeping, andprovides the basis for additional ways to identify ‘suspiciousactivities’ involving cash that can occur.

In comparison, Hyperlabel tags can be produced at a low cost. They canbe printed all over the surface of a note (redundancy) and they are easyto read. The IR ink ‘tags’ will not be damaged by folding, washing,physical impact or electrostatic shock, and cannot be torn out of thenote. They can be used and read in the presence of radiopaque materials.They support omnidirectional reading, as well as very low cost proximityreaders. Hyperlabel tags cannot be read while in the wallets ofcitizens, so do not present a threat of covert scanning providinginformation to criminals. This should make Hyperlabel tagged currencyacceptable to privacy advocates concerned about the ability to readnotes without the knowledge of the owner. They also meet current andanticipated regulations and guidelines for national and internationalagencies. An overview of the key components of a Hyperlabel systemneeded to achieve these objectives is provided in the next section.

Socioeconomic Consequences

Although there are significant advantages in implementing a Hyperlabelsolution, there are also socioeconomic consequences that need to benoted.

Of primary concern is the consequence of Hyperlabel becoming a pervasivecounterfeit detection and cash flow tracking system. This couldeffectively and materially hamper the activities of organized crime andterrorists relying on counterfeiting or laundering cash and it couldprove to be disruptive as criminals find alternative methods to supporttheir activities.

In this context, further questions ought to be considered beforeproceeding with implementation.

Some of these include:

-   -   Will crime move to less regulated and less developed nations        causing further decline in their socioeconomic status?    -   Will electronic crime become more sophisticated?    -   How will Hyperlabel alter the structure of criminal and        terrorist networks?    -   The cash economy is often used by small businesses as a form of        tax evasion—what, if anything, will replace this once cash        becomes traceable?        Related Applications

The Hyperlabel infrastructure can also be used to validate and trackother ‘secure documents’ where the value of the document is based uponwhat it represents, rather than what it contains.

Some examples are:

-   -   Government checks    -   Bank issued checks    -   Bearer bonds    -   Stock certificates    -   Lottery tickets    -   Event tickets    -   Passports    -   Medical certificates    -   Postage stamps    -   Food stamps

The Hyperlabel infrastructure is also shared with other applications,such as grocery tracking and interactive documents.

1. A sensing device for use with a security document, the securitydocument having disposed thereon or therein coded data including aplurality of coded data portions, each coded data portion beingindicative of an identity of the security document and a signature part,the signature part being a part of a digital signature of at least theidentity, the sensing device including: a sensor for sensing a pluralityof coded data portions; and, a processor for: determining, using sensedcoded data portions, a sensed identity, a plurality of signature parts,and an identifier for each signature part; generating a sensed signaturefrom the plurality of signature parts by arranging signature partsaccording to respective identifiers; determining a generated identityfrom the sensed signature; and authenticating the security document bycomparing the sensed identity and the generated identity.
 2. A sensingdevice according to claim 1, wherein the sensing device further includesan indicator for indicating the sensed identity of the securitydocument.
 3. A sensing device according to claim 1, wherein theprocessor further: generates, using the sensed identity and a key, anduses the key to determine the generated identity from the sensedsignature.
 4. A sensing device according to claim 1, wherein the digitalsignature is a digital signature of the identity and at least part ofpredetermined padding, the padding being at least one of: apredetermined number; and, a random number.
 5. A sensing deviceaccording to claim 1, wherein the processor further: accesses, using thesensed identity, tracking data indicative of, for each of a number ofexisting security documents: the identity of the security document; and,tracking information indicative of the location of the securitydocument; and, at least one of: determines, using the trackinginformation, if the security document is a duplicate of one of theexisting security documents; and, updates the tracking information.
 6. Asensing device according to claim 1, wherein the coded data issubstantially invisible to an unaided human.
 7. A sensing deviceaccording to claim 1, wherein the coded data is printed on the surfaceusing at least one of: an invisible ink; and, an infrared-absorptiveink.
 8. A sensing device according to claim 1, wherein the coded data isprovided substantially coincident with visible human-readableinformation.
 9. A sensing device according to claim 1, wherein at leastsome of the coded data portions encode at least one of: a location ofthe respective coded data portion; a position of the respective codeddata portion on the surface; a size of the coded data portions; and,units of indicated locations.
 10. A sensing device according to claim 1,wherein the coded data includes at least one of: redundant data; dataallowing error correction; Reed-Solomon data; and, Cyclic RedundancyCheck (CRC) data.
 11. A sensing device according to claim 1, wherein thesecurity document is at least one of: a currency note; a check; a creditor debit card; a redeemable ticket, voucher, or coupon; a lottery ticketor instant win ticket; and, an identity card or document.
 12. A sensingdevice according to claim 1, wherein the identity is indicative of atleast one of: a currency note attribute including at least one of:currency; issue country; denomination; note side; printing works; andserial number; a check attribute including at least one of: currency;issuing institution; account number; serial number; expiry date; checkvalue; and limit; a card attribute including at least one of: card type;issuing institution; account number; issue date; expiry date; and limit.13. A sensing device according to claim 1, wherein the coded data isarranged in accordance with at least one layout having n-fold rotationalsymmetry, where n is at least two, the layout including n identicalsub-layouts rotated 1/n revolutions apart about a centre of rotation, atleast one sub-layout including rotation-indicating data thatdistinguishes that sub-layout from each other sub-layout.
 14. A sensingdevice according to claim 1, wherein the coded data is arranged inaccordance with at least one layout having n-fold rotational symmetry,where n is at least two, the layout encoding orientation-indicating datacomprising a sequence of an integer multiple m of n symbols, where m isone or more, each encoded symbol being distributed at n locations abouta centre of rotational symmetry of the layout such that decoding thesymbols at each of the n orientations of the layout produces nrepresentations of the orientation-indicating data, each representationcomprising a different cyclic shift of the orientation-indicating dataand being indicative of the degree of rotation of the layout.